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| author | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
|---|---|---|
| committer | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
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diff --git a/articles/cowboy2-qs/index.html b/articles/cowboy2-qs/index.html new file mode 100644 index 00000000..576bb4d7 --- /dev/null +++ b/articles/cowboy2-qs/index.html @@ -0,0 +1,308 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Cowboy 2.0 and query strings</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Cowboy 2.0 and query strings</span></h1> + <p class="date"> + <span class="day">20</span> + <span class="month">Aug</span> + </p> +</header> + +<div class="paragraph"><p>Now that Cowboy 1.0 is out, I can spend some of my time thinking
+about Cowboy 2.0 that will be released soon after Erlang/OTP 18.0.
+This entry discusses the proposed changes to query string handling
+in Cowboy.</p></div>
+<div class="paragraph"><p>Cowboy 2.0 will respond to user wishes by simplifying the interface
+of the <code>cowboy_req</code> module. Users want two things: less
+juggling with the Req variable, and more maps. Maps is the only
+dynamic key/value data structure in Erlang that we can match directly
+to extract values, allowing users to greatly simplify their code as
+they don’t need to call functions to do everything anymore.</p></div>
+<div class="paragraph"><p>Query strings are a good candidate for maps. It’s a list of
+key/values, so it’s pretty obvious we can win a lot by using maps.
+However query strings have one difference with maps: they can have
+duplicate keys.</p></div>
+<div class="paragraph"><p>How are we expected to handle duplicate keys? There’s no standard
+behavior. It’s up to applications. And looking at what is done in
+the wild, there’s no de facto standard either. While some ignore
+duplicate keys (keeping the first or the last they find), others
+require duplicate keys to end with <code>[]</code> to automatically
+put the values in a list, or even worse, languages like PHP even
+allow you to do things like <code>key[something][other]</code> and
+create a deep structure for it. Finally some allow any key to have
+duplicates and just gives you lists of key/values.</p></div>
+<div class="paragraph"><p>Cowboy so far had functions to retrieve query string values one
+value at a time, and if there were duplicates it would return the
+first it finds. It also has a function returning the entire list
+with all duplicates, allowing you to filter it to get all of them,
+and another function that returns the raw query string.</p></div>
+<div class="paragraph"><p>What are duplicates used for? Not that many things actually.</p></div>
+<div class="paragraph"><p>One use of duplicate keys is with HTML forms. It is common practice
+to give all related checkboxes the same name so you get a list of
+what’s been checked. When nothing is checked, nothing is sent at all,
+the key is not in the list.</p></div>
+<div class="paragraph"><p>Another use of duplicate keys is when generating forms. A good
+example of that would be a form that allows uploading any number
+of files. When you add a file, client-side code adds another field
+to the form. Repeat up to a certain limit.</p></div>
+<div class="paragraph"><p>And that’s about it. Of note is that HTML radio elements share
+the same name too, but only one key/value is sent, so they are not
+relevant here.</p></div>
+<div class="paragraph"><p>Normally this would be the part where I tell you how we solve
+this elegantly. But I had doubts. Why? Because there’s no good
+solutions to solving only this particular problem.</p></div>
+<div class="paragraph"><p>I then stopped thinking about duplicate keys for a minute and
+started to think about the larger problem.</p></div>
+<div class="paragraph"><p>Query strings are input data. They take a particular form,
+and may be sent as part of the URI or as part of the request
+body. We have other kinds of input data. We have headers and
+cookies and the request body in various forms. We also have
+path segments in URIs.</p></div>
+<div class="paragraph"><p>What do you do with input data? Well you use it to do
+something. But there is one thing that you almost always do
+(and if you don’t, you really should): you validate it and
+you map it into Erlang terms.</p></div>
+<div class="paragraph"><p>Cowboy left the user take care of validation and conversion
+into Erlang terms so far. Rather, it left the user take care
+of it everywhere except one place. Guess where? That’s right,
+bindings.</p></div>
+<div class="paragraph"><p>If you define routes with bindings then you have the option
+to provide constraints. Constraints can be used to do two things:
+validate the data and convert it in a more appropriate term. For
+example if you use the <code>int</code> constraint, Cowboy will
+make sure the binding is an integer, and will replace the value
+with the integer representation so that you can use it directly.
+In this particular case it not only routes the URI, but also
+validates and converts the bindings directly.</p></div>
+<div class="paragraph"><p>This is very relevant in the case of our duplicate keys,
+because if we have a list with duplicates of a key, chances
+are we want to convert that into a list of Erlang terms, and
+also make sure that all the elements in this list are expected.</p></div>
+<div class="paragraph"><p>The answer to this particular problem is simple. We need a
+function that will parse the query string and apply constraints.
+But this is not all, there is one other problem to be solved.</p></div>
+<div class="paragraph"><p>The other problem is that for the user some keys are mandatory
+and some are optional. Optional keys include the ones that
+correspond to HTML checkboxes: if the key for one or more
+checkbox is missing from the query string, we still want to
+have an empty list in our map so we can easily match. Matching
+maps is great, but not so much when values might be missing,
+so we have to normalize this data a little.</p></div>
+<div class="paragraph"><p>This problem is solved by allowing a default value. If the
+key is missing and a default exists, set it. If no default
+exists, then the key was mandatory and we want to crash.</p></div>
+<div class="paragraph"><p>I therefore make a proposal for changing the query string
+interface to three functions.</p></div>
+<div class="paragraph"><p>The first function already exists, it is <code>cowboy_req:qs(Req)</code>
+and it returns only the query string binary. No more Req returned.</p></div>
+<div class="paragraph"><p>The second function is a renaming of <code>cowboy_req:qs_vals(Req)</code>
+to something more explicit: <code>cowboy_req:parse_qs(Req)</code>.
+The new name implies that a parsing operation is done. It was implicit
+and cached before. It will be explicit and not cached anymore now.
+Again, no more Req returned.</p></div>
+<div class="paragraph"><p>The third function is the one I mentioned above. I think
+the interface <code>cowboy_req:match_qs(Req, Fields)</code> is
+most appropriate. It returns a normalized map that is the same
+regardless of optional fields being provided with the request,
+allowing for easy matching. It crashes if something went wrong.
+Still no Req returned.</p></div>
+<div class="paragraph"><p>I feel that this three function interface provides everything
+one would need to comfortably write applications. You can get
+low level and get the query string directly; you can get a list
+of key/value binaries without any additional processing and do it
+on your own; or you can get a processed map that contains Erlang
+terms ready to be used.</p></div>
+<div class="paragraph"><p>I strongly believe that by democratizing the constraints to
+more than just bindings, but also to query string, cookies and
+other key/values in Cowboy, we can allow the developer to quickly
+and easily go from HTTP request to Erlang function calls. The
+constraints are reusable functions that can serve as guards
+against unwanted data, providing convenience in the process.</p></div>
+<div class="paragraph"><p>Your handlers will not look like an endless series of calls
+to get and convert the input data, they will instead be just
+one call at the beginning followed by the actual application
+logic, thanks to constraints and maps.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span>
+ #{<span style="color: #FF6600">name</span><span style="color: #990000">:=</span><span style="color: #009900">Name</span>, <span style="color: #FF6600">email</span><span style="color: #990000">:=</span><span style="color: #009900">Email</span>, <span style="color: #FF6600">choices</span><span style="color: #990000">:=</span><span style="color: #009900">ChoicesList</span>, <span style="color: #FF6600">remember_me</span><span style="color: #990000">:=</span><span style="color: #009900">RememberMe</span>} <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>(<span style="color: #009900">Req</span>, [
+ <span style="font-weight: bold"><span style="color: #000080">name</span></span>, {<span style="color: #FF6600">email</span>, <span style="color: #FF6600">email</span>},
+ {<span style="color: #FF6600">choices</span>, <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> <span style="font-weight: bold"><span style="color: #000000">check_choices</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>, []},
+ {<span style="color: #FF6600">remember_me</span>, <span style="color: #FF6600">boolean</span>, <span style="color: #000080">false</span>}]),
+ <span style="font-weight: bold"><span style="color: #000000">save_choices</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>, <span style="color: #009900">ChoicesList</span>),
+ <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">RememberMe</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">create_account</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>); <span style="color: #000080">true</span> <span style="color: #990000">-></span> <span style="color: #FF6600">ok</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"blue"</span><span style="color: #990000">>></span>) <span style="color: #990000">-></span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">blue</span>};
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000"><<</span><span style="color: #FF0000">"red"</span><span style="color: #990000">>></span>) <span style="color: #990000">-></span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">red</span>};
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">_</span>) <span style="color: #990000">-></span> <span style="color: #000080">false</span>;</tt></pre></div></div>
+<div class="paragraph"><p>(Don’t look too closely at the structure yet.)</p></div>
+<div class="paragraph"><p>As you can see in the above snippet, it becomes really easy
+to go from query string to values. You can also use the map
+directly as it is guaranteed to only contain the keys you
+specified, any extra key is not returned.</p></div>
+<div class="paragraph"><p>This would I believe be a huge step up as we can now
+focus on writing applications instead of translating HTTP
+calls. Cowboy can now take care of it.</p></div>
+<div class="paragraph"><p>And to conclude, this also solves our duplicate keys
+dilemma, as they now automatically become a list of binaries,
+and this list is then checked against constraints that
+will fail if they were not expecting a list. And in the
+example above, it even converts the values to atoms for
+easier manipulation.</p></div>
+<div class="paragraph"><p>As usual, feedback is more than welcome, and I apologize
+for the rocky structure of this post as it contains all the
+thoughts that went into this rather than just the conclusion.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/erlang-scalability/index.html b/articles/erlang-scalability/index.html new file mode 100644 index 00000000..6acc3e87 --- /dev/null +++ b/articles/erlang-scalability/index.html @@ -0,0 +1,293 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Erlang Scalability</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Erlang Scalability</span></h1> + <p class="date"> + <span class="day">18</span> + <span class="month">Feb</span> + </p> +</header> + +<div class="paragraph"><p>I would like to share some experience and theories on
+Erlang scalability.</p></div>
+<div class="paragraph"><p>This will be in the form of a series of hints, which
+may or may not be accompanied with explanations as to why
+things are this way, or how they improve or reduce the scalability
+of a system. I will try to do my best to avoid giving falsehoods,
+even if that means a few things won’t be explained.</p></div>
+<div class="sect1">
+<h2 id="_nifs">NIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>NIFs are considered harmful. I don’t know any single NIF-based
+library that I would recommend. That doesn’t mean they should
+all be avoided, just that if you’re going to want your system to
+scale, you probably shouldn’t use a NIF.</p></div>
+<div class="paragraph"><p>A common case for using NIFs is JSON processing. The problem
+is that JSON is a highly inefficient data structure (similar
+in inefficiency to XML, although perhaps not as bad). If you can
+avoid using JSON, you probably should. MessagePack can replace
+it in many situations.</p></div>
+<div class="paragraph"><p>Long-running NIFs will take over a scheduler and prevent Erlang
+from efficiently handling many processes.</p></div>
+<div class="paragraph"><p>Short-running NIFs will still confuse the scheduler if they
+take more than a few microseconds to run.</p></div>
+<div class="paragraph"><p>Threaded NIFs, or the use of the <code>enif_consume_timeslice</code>
+might help allievate this problem, but they’re not a silver bullet.</p></div>
+<div class="paragraph"><p>And as you already know, a crashing NIF will take down your VM,
+destroying any claims you may have at being scalable.</p></div>
+<div class="paragraph"><p>Never use a NIF because "C is fast". This is only true in
+single-threaded programs.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_bifs">BIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>BIFs can also be harmful. While they are generally better than
+NIFs, they are not perfect and some of them might have harmful
+effects on the scheduler.</p></div>
+<div class="paragraph"><p>A great example of this is the <code>erlang:decode_packet/3</code>
+BIF, when used for HTTP request or response decoding. Avoiding
+its use in <em>Cowboy</em> allowed us to see a big increase in
+the number of requests production systems were able to handle,
+up to two times the original amount. Incidentally this is something
+that is impossible to detect using synthetic benchmarks.</p></div>
+<div class="paragraph"><p>BIFs that return immediately are perfectly fine though.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_binary_strings">Binary strings</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Binary strings use less memory, which means you spend less time
+allocating memory compared to list-based strings. They are also
+more natural for strings manipulation because they are optimized
+for appending (as opposed to prepending for lists).</p></div>
+<div class="paragraph"><p>If you can process a binary string using a single match context,
+then the code will run incredibly fast. The effects will be much
+increased if the code was compiled using HiPE, even if your Erlang
+system isn’t compiled natively.</p></div>
+<div class="paragraph"><p>Avoid using <code>binary:split</code> or <code>binary:replace</code>
+if you can avoid it. They have a certain overhead due to supporting
+many options that you probably don’t need for most operations.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_buffering_and_streaming">Buffering and streaming</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Use binaries. They are great for appending, and it’s a direct copy
+from what you receive from a stream (usually a socket or a file).</p></div>
+<div class="paragraph"><p>Be careful to not indefinitely receive data, as you might end up
+having a single binary taking up huge amounts of memory.</p></div>
+<div class="paragraph"><p>If you stream from a socket and know how much data you expect,
+then fetch that data in a single <code>recv</code> call.</p></div>
+<div class="paragraph"><p>Similarly, if you can use a single <code>send</code> call, then
+you should do so, to avoid going back and forth unnecessarily between
+your Erlang process and the Erlang port for your socket.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_list_and_binary_comprehensions">List and binary comprehensions</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Prefer list comprehensions over <code>lists:map/2</code>. The
+compiler will be able to optimize your code greatly, for example
+not creating the result if you don’t need it. As time goes on,
+more optimizations will be added to the compiler and you will
+automatically benefit from them.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_gen_server_is_no_silver_bullet">gen_server is no silver bullet</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>It’s a bad idea to use <code>gen_server</code> for everything.
+For two reasons.</p></div>
+<div class="paragraph"><p>There is an overhead everytime the <code>gen_server</code> receives
+a call, a cast or a simple message. It can be a problem if your
+<code>gen_server</code> is in a critical code path where speed
+is all that matters. Do not hesitate to create other kinds of
+processes where it makes sense. And depending on the kind of process,
+you might want to consider making them special processes, which
+would essentially behave the same as a <code>gen_server</code>.</p></div>
+<div class="paragraph"><p>A common mistake is to have a unique <code>gen_server</code> to
+handle queries from many processes. This generally becomes the
+biggest bottleneck you’ll want to fix. You should try to avoid
+relying on a single process, using a pool if you can.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_supervisor_and_monitoring">Supervisor and monitoring</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>A <code>supervisor</code> is also a <code>gen_server</code>,
+so the previous points also apply to them.</p></div>
+<div class="paragraph"><p>Sometimes you’re in a situation where you have supervised
+processes but also want to monitor them in one or more other
+processes, effectively duplicating the work. The supervisor
+already knows when processes die, why not use this to our
+advantage?</p></div>
+<div class="paragraph"><p>You can create a custom supervisor process that will perform
+both the supervision and handle exit and other events, allowing
+to avoid the combination of supervising and monitoring which
+can prove harmful when many processes die at once, or when you
+have many short lived processes.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_ets_for_lolspeed_tm">ets for LOLSPEED(tm)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>If you have data queried or modified by many processes, then
+<code>ets</code> public or protected tables will give you the
+performance boost you require. Do not forget to set the
+<code>read_concurrency</code> or <code>write_concurrency</code>
+options though.</p></div>
+<div class="paragraph"><p>You might also be thrilled to know that Erlang R16B will feature
+a big performance improvement for accessing <code>ets</code> tables
+concurrently.</p></div>
+</div>
+</div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/erlang-validate-utf8/index.html b/articles/erlang-validate-utf8/index.html new file mode 100644 index 00000000..3e616c01 --- /dev/null +++ b/articles/erlang-validate-utf8/index.html @@ -0,0 +1,344 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Validating UTF-8 binaries with Erlang</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Validating UTF-8 binaries with Erlang</span></h1> + <p class="date"> + <span class="day">06</span> + <span class="month">Mar</span> + </p> +</header> + +<div class="paragraph"><p>Yesterday I pushed Websocket permessage-deflate to
+Cowboy master. I also pushed
+<a href="https://github.com/ninenines/cowlib/commit/7e4983b70ddf8cedb967e36fba6a600731bdad5d">a
+change in the way the code validates UTF-8 data</a>
+(required for text and close frames as per the spec).</p></div>
+<div class="paragraph"><p>When looking into why the permessage-deflate tests
+in autobahntestsuite were taking such a long time, I
+found that autobahn is using an adaptation of the
+algorithm named <a href="http://bjoern.hoehrmann.de/utf-8/decoder/dfa/">Flexible
+and Economical UTF-8 Decoder</a>. This is the C99
+implementation:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-style: italic"><span style="color: #9A1900">// Copyright (c) 2008-2009 Bjoern Hoehrmann <[email protected]></span></span>
+<span style="font-style: italic"><span style="color: #9A1900">// See http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.</span></span>
+
+<span style="font-weight: bold"><span style="color: #000080">#define</span></span> UTF8_ACCEPT <span style="color: #993399">0</span>
+<span style="font-weight: bold"><span style="color: #000080">#define</span></span> UTF8_REJECT <span style="color: #993399">1</span>
+
+<span style="font-weight: bold"><span style="color: #0000FF">static</span></span> <span style="font-weight: bold"><span style="color: #0000FF">const</span></span> <span style="color: #008080">uint8_t</span> utf8d<span style="color: #990000">[]</span> <span style="color: #990000">=</span> <span style="color: #FF0000">{</span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 00..1f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 20..3f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 40..5f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 60..7f</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 80..9f</span></span>
+ <span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// a0..bf</span></span>
+ <span style="color: #993399">8</span><span style="color: #990000">,</span><span style="color: #993399">8</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// c0..df</span></span>
+ <span style="color: #993399">0xa</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x4</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// e0..ef</span></span>
+ <span style="color: #993399">0xb</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x5</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// f0..ff</span></span>
+ <span style="color: #993399">0x0</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x2</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x5</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x7</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x4</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s0..s0</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s1..s2</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s3..s4</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s5..s6</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s7..s8</span></span>
+<span style="color: #FF0000">}</span><span style="color: #990000">;</span>
+
+uint32_t inline
+<span style="font-weight: bold"><span style="color: #000000">decode</span></span><span style="color: #990000">(</span>uint32_t<span style="color: #990000">*</span> state<span style="color: #990000">,</span> uint32_t<span style="color: #990000">*</span> codep<span style="color: #990000">,</span> <span style="color: #008080">uint32_t</span> byte<span style="color: #990000">)</span> <span style="color: #FF0000">{</span>
+ <span style="color: #008080">uint32_t</span> type <span style="color: #990000">=</span> utf8d<span style="color: #990000">[</span>byte<span style="color: #990000">];</span>
+
+ <span style="color: #990000">*</span>codep <span style="color: #990000">=</span> <span style="color: #990000">(*</span>state <span style="color: #990000">!=</span> UTF8_ACCEPT<span style="color: #990000">)</span> <span style="color: #990000">?</span>
+ <span style="color: #990000">(</span>byte <span style="color: #990000">&</span> <span style="color: #993399">0x3fu</span><span style="color: #990000">)</span> <span style="color: #990000">|</span> <span style="color: #990000">(*</span>codep <span style="color: #990000"><<</span> <span style="color: #993399">6</span><span style="color: #990000">)</span> <span style="color: #990000">:</span>
+ <span style="color: #990000">(</span><span style="color: #993399">0xff</span> <span style="color: #990000">>></span> type<span style="color: #990000">)</span> <span style="color: #990000">&</span> <span style="color: #990000">(</span>byte<span style="color: #990000">);</span>
+
+ <span style="color: #990000">*</span>state <span style="color: #990000">=</span> utf8d<span style="color: #990000">[</span><span style="color: #993399">256</span> <span style="color: #990000">+</span> <span style="color: #990000">*</span>state<span style="color: #990000">*</span><span style="color: #993399">16</span> <span style="color: #990000">+</span> type<span style="color: #990000">];</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">return</span></span> <span style="color: #990000">*</span>state<span style="color: #990000">;</span>
+<span style="color: #FF0000">}</span></tt></pre></div></div>
+<div class="paragraph"><p>And this is the Erlang implementation I came up with:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-style: italic"><span style="color: #9A1900">%% This function returns 0 on success, 1 on error, and 2..8 on incomplete data.</span></span>
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<>></span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span> <span style="color: #009900">State</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">128</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">144</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">144</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">144</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">144</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">8</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">144</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">192</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">192</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">4</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">192</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">192</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">192</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">194</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">224</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">224</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">4</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">225</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">237</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">237</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">5</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">238</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">239</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">240</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">6</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">241</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">242</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">243</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">7</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">244</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">8</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">_</span>, <span style="color: #990000">_</span>) <span style="color: #990000">-></span> <span style="color: #993399">1</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Does it look similar to you? So how did we get there?</p></div>
+<div class="paragraph"><p>I started with a naive implementation of the original. First, we
+don’t need the codepoint calculated and extracted for our validation
+function. We just want to know the data is valid, so we only need to
+calculate the next state. Then, the only thing we needed to be careful
+about was that tuples are 1-based, and that we need to stop processing
+the binary when we get the state 1 or when the binary is empty.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<>></span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span> <span style="color: #009900">State</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">_</span>, <span style="color: #993399">1</span>) <span style="color: #990000">-></span> <span style="color: #993399">1</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #009900">State</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">257</span> <span style="color: #990000">+</span> <span style="color: #009900">State</span> <span style="color: #990000">*</span> <span style="color: #993399">16</span> <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">1</span> <span style="color: #990000">+</span> <span style="color: #009900">C</span>, <span style="font-weight: bold"><span style="color: #000080">?UTF8D</span></span>), <span style="font-weight: bold"><span style="color: #000080">?UTF8D</span></span>))<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The macro <code>?UTF8D</code> is the tuple equivalent of the C array
+in the original code.</p></div>
+<div class="paragraph"><p>Compared to our previous algorithm, this performed about the same.
+In some situations a little faster, in some a little slower. In other words,
+not good enough. But because this new algorithm allows us to avoid a binary
+concatenation this warranted looking further.</p></div>
+<div class="paragraph"><p>It was time to step into crazy land.</p></div>
+<div class="paragraph"><p>Erlang is very good at pattern matching, even more so than doing some
+arithmetic coupled by fetching elements from a tuple. So I decided I was
+going to write all possible clauses for all combinations of <code>C</code>
+and <code>State</code>. And by write I mean generate.</p></div>
+<div class="paragraph"><p>So I opened my Erlang shell, defined the variable <code>D</code> to be
+the tuple <code>?UTF8D</code> with its 400 elements, and then ran the
+following expression (after a bit of trial and error):</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">16</span><span style="color: #990000">></span> <span style="font-weight: bold"><span style="color: #000000">file:write_file</span></span>(<span style="color: #FF0000">"out.txt"</span>,
+ [<span style="font-weight: bold"><span style="color: #000000">io_lib:format</span></span>(<span style="color: #FF0000">"validate_utf8(<< ~p, Rest/bits >>, ~p) -> ~p;~n"</span>,
+ [<span style="color: #009900">C</span>, <span style="color: #009900">S</span>, <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">257</span> <span style="color: #990000">+</span> <span style="color: #009900">S</span> <span style="color: #990000">*</span> <span style="color: #993399">16</span> <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">1</span> <span style="color: #990000">+</span> <span style="color: #009900">C</span>, <span style="color: #009900">D</span>), <span style="color: #009900">D</span>)])
+ || <span style="color: #009900">C</span> <span style="color: #990000"><-</span> <span style="font-weight: bold"><span style="color: #000000">lists:seq</span></span>(<span style="color: #993399">0</span>,<span style="color: #993399">255</span>), <span style="color: #009900">S</span> <span style="color: #990000"><-</span> <span style="font-weight: bold"><span style="color: #000000">lists:seq</span></span>(<span style="color: #993399">0</span>,<span style="color: #993399">8</span>)])<span style="color: #990000">.</span>
+<span style="color: #FF6600">ok</span></tt></pre></div></div>
+<div class="paragraph"><p>The result is a 2304 lines long file, containing 2304 clauses.
+People who pay attention to what I say on Twitter will remember
+I said something around 3000 clauses, but that was just me not
+using the right number of states in my estimate.</p></div>
+<div class="paragraph"><p>There was a little more work to be done on this generated
+code that I did using regular expressions. We need to recurse
+when the resulting state is not 1. We also need to stop when
+the binary is empty, making it the 2305th clause.</p></div>
+<div class="paragraph"><p>Still, 2305 is a lot. But hey, the code did work, and faster
+than the previous implementation too! But hey, perhaps I could
+find a way to reduce its size.</p></div>
+<div class="paragraph"><p>Removing all the clauses that return 1 and putting a catch-all
+clause at the end instead reduced the number to about 500, and
+showed that many clauses were similar:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">0</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">1</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">2</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">3</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">4</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">5</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">6</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">7</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);</tt></pre></div></div>
+<div class="paragraph"><p>But also:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">5</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">6</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">5</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">6</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);</tt></pre></div></div>
+<div class="paragraph"><p>Patterns, my favorites!</p></div>
+<div class="paragraph"><p>A little more time was spent to edit the 500 or so clauses into
+smaller equivalents, testing that performance was not impacted, and
+comitting the result.</p></div>
+<div class="paragraph"><p>The patterns above can be found here in the resulting function:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">128</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="color: #990000">...</span>
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000"><<</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">>></span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">>=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000"><</span> <span style="color: #993399">160</span> <span style="color: #990000">-></span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="color: #990000">...</span></tt></pre></div></div>
+<div class="paragraph"><p>I hope you enjoyed this post.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/erlang.mk-and-relx/index.html b/articles/erlang.mk-and-relx/index.html new file mode 100644 index 00000000..bbaff768 --- /dev/null +++ b/articles/erlang.mk-and-relx/index.html @@ -0,0 +1,271 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Build Erlang releases with Erlang.mk and Relx</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link 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href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Build Erlang releases with Erlang.mk and Relx</span></h1> + <p class="date"> + <span class="day">28</span> + <span class="month">May</span> + </p> +</header> + +<div class="paragraph"><p>Building OTP releases has always been a difficult task. Tools like
+Reltool or Rebar have made this simpler, but
+it’s no panacea. This article will show you an alternative and
+hopefully much simpler solution.</p></div>
+<div class="paragraph"><p>There is two steps to building a release. First you need to build
+the various OTP applications you want to include in the release. Once
+done, you need to create the release itself, by including the Erlang
+runtime system alongside the applications, a boot script to start the
+node and all its applications, and some configuration files.</p></div>
+<div class="paragraph"><p><a href="https://github.com/extend/erlang.mk">Erlang.mk</a> solves
+the first step. It is an include file for GNU Make. Just
+including it in a Makefile is enough to allow building your project,
+fetching and building dependencies, building documentation, performing
+static analysis and more.</p></div>
+<div class="paragraph"><p><a href="https://github.com/erlware/relx">Relx</a> solves the second
+step. It is a release creation tool, wrapped into a single executable
+file. It doesn’t require a configuration file. And if you do need one,
+it will be a pretty small one.</p></div>
+<div class="paragraph"><p>Let’s take a look at the smallest Erlang.mk powered
+Makefile. There is only one thing required: defining the project
+name.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PROJECT =</span> my_project
+
+include erlang.mk</tt></pre></div></div>
+<div class="paragraph"><p>Simply doing this allows you to build your application by typing
+<code>make</code>, running tests using <code>make tests</code>, and
+more. It will even compile your <em>.dtl</em> files found in the
+<em>templates/</em> directory if you are using ErlyDTL!</p></div>
+<div class="paragraph"><p>Let’s now take a look at a simplified version of the Makefile for
+this website. I only removed a few targets that were off-topic.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PROJECT =</span> ninenines
+
+<span style="color: #009900">DEPS =</span> cowboy erlydtl
+<span style="color: #009900">dep_cowboy =</span> https<span style="color: #990000">:</span>//github.com/extend/cowboy.git 0.8.5
+<span style="color: #009900">dep_erlydtl =</span> https<span style="color: #990000">:</span>//github.com/evanmiller/erlydtl.git 4d0dc8fb
+
+<span style="font-weight: bold"><span style="color: #000080">.PHONY:</span></span> release clean-release
+
+<span style="color: #990000">release:</span> clean-release all projects
+ relx -o rel<span style="color: #990000">/</span><span style="color: #009900">$(PROJECT)</span>
+
+<span style="color: #990000">clean-release:</span> clean-projects
+ rm -rf rel<span style="color: #990000">/</span><span style="color: #009900">$(PROJECT)</span>
+
+include erlang.mk</tt></pre></div></div>
+<div class="paragraph"><p>You can see here how to define dependencies. First you list all
+the dependency names, then you have one line per dependency, giving
+the repository URL and the commit number, tag or branch you want.</p></div>
+<div class="paragraph"><p>Then you can see two targets defined, with <code>release</code>
+becoming the default target, because it was defined first. You can
+override the default target <code>all</code>, which builds the
+application and its dependencies, this way.</p></div>
+<div class="paragraph"><p>And as you can see, the <code>release</code> target uses
+Relx to build a release into the <em>rel/ninenines/</em>
+directory. Let’s take a look at the configuration file for this release.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">release</span>, {<span style="color: #FF6600">ninenines</span>, <span style="color: #FF0000">"1"</span>}, [<span style="color: #FF6600">ninenines</span>]}<span style="color: #990000">.</span>
+
+{<span style="color: #FF6600">extended_start_script</span>, <span style="color: #000080">true</span>}<span style="color: #990000">.</span>
+{<span style="color: #FF6600">sys_config</span>, <span style="color: #FF0000">"rel/sys.config"</span>}<span style="color: #990000">.</span>
+
+{<span style="color: #FF6600">overlay</span>, [
+ {<span style="color: #FF6600">mkdir</span>, <span style="color: #FF0000">"log"</span>},
+ {<span style="color: #FF6600">copy</span>, <span style="color: #FF0000">"rel/vm.args"</span>,
+ <span style="color: #FF0000">"releases/\{\{release_name\}\}-\{\{release_version\}\}/vm.args"</span>}
+]}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The first line defines a release named <code>ninenines</code>, which
+has a version number <code>"1"</code> and includes one application, also
+named <code>ninenines</code>, although it doesn’t have to.</p></div>
+<div class="paragraph"><p>We then use the <code>extended_start_script</code> option to tell
+Relx that we would like to have a start script that allows
+us to not only start the release, but do so with the node in the
+background, or also to allow us to connect to a running node, and so on.
+This start script has the same features as the one tools like
+Rebar generates.</p></div>
+<div class="paragraph"><p>The rest of the file just makes sure our configuration files are
+where we expect them. Relx will automatically take care
+of your <em>sys.config</em> file as long as you tell it where to
+find it. The <em>vm.args</em> file used by the extended start script
+needs to be handled more explicitly by using an overlay however.</p></div>
+<div class="paragraph"><p>How does Relx find what applications to include?
+By looking at the application dependencies in the <em>.app</em>
+file of each OTP application. Make sure you put all dependencies in
+there, <em>including</em> library applications, and Relx
+will find everything for you.</p></div>
+<div class="paragraph"><p>For example, this release includes the following applications.
+Only what’s strictly required.</p></div>
+<div class="listingblock">
+<div class="content">
+<pre><code>compiler-4.9.1 crypto-2.3 kernel-2.16.1 ranch-0.8.3 syntax_tools-1.6.11
+cowboy-0.8.5 erlydtl-0.7.0 ninenines-0.2.0 stdlib-1.19.1</code></pre>
+</div></div>
+<div class="paragraph"><p>The <em>sys.config</em> file is standard and
+<a href="http://www.erlang.org/doc/man/config.html">well documented</a>.
+The <em>vm.args</em> file is just an optionally multiline file
+containing all the flags to pass to the Erlang VM, for example
+<code>-name [email protected] -heart</code>.</p></div>
+<div class="paragraph"><p>Building OTP releases has always been a difficult task. Until now.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/erlanger-playbook-september-2015-update/index.html b/articles/erlanger-playbook-september-2015-update/index.html new file mode 100644 index 00000000..66dcd309 --- /dev/null +++ b/articles/erlanger-playbook-september-2015-update/index.html @@ -0,0 +1,172 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: The Erlanger Playbook September 2015 Update</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>The Erlanger Playbook September 2015 Update</span></h1> + <p class="date"> + <span class="day">02</span> + <span class="month">Sep</span> + </p> +</header> + +<div class="paragraph"><p>An update to The Erlanger Playbook is now available!</p></div>
+<div class="paragraph"><p>The Erlanger Playbook is a book about software development using
+Erlang. It currently covers all areas from the conception, design,
+the writing of code, documentation and tests.</p></div>
+<div class="paragraph"><p>The book is still a work in progress. Future topics will include
+refactoring, debugging and tracing, benchmarking, releases, community
+management (for open source projects).</p></div>
+<div class="paragraph"><p>This update fixes a number of things and adds two chapters: IOlists
+and Erlang building blocks.</p></div>
+<div class="paragraph"><p>Learn more about <a href="/articles/erlanger-playbook">The Erlanger Playbook</a>!</p></div>
+<div class="paragraph"><p>This is a self-published ebook. The base price is 50€. All proceeds
+will be used to allow me to work on open source full time.</p></div>
+<div class="paragraph"><p>Thank you for helping me helping you help us all!</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/erlanger-playbook/index.html b/articles/erlanger-playbook/index.html new file mode 100644 index 00000000..bf67e77e --- /dev/null +++ b/articles/erlanger-playbook/index.html @@ -0,0 +1,225 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: The Erlanger Playbook</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>The Erlanger Playbook</span></h1> + <p class="date"> + <span class="day">18</span> + <span class="month">Jun</span> + </p> +</header> + +<div class="paragraph"><p>I am proud to announce the pre-release of The Erlanger Playbook.</p></div>
+<div class="paragraph"><p>The Erlanger Playbook is a book about software development using
+Erlang. It currently covers all areas from the conception, design,
+the writing of code, documentation and tests.</p></div>
+<div class="paragraph"><p>The book is still a work in progress. Future topics will include
+refactoring, debugging and tracing, benchmarking, releases, community
+management (for open source projects).</p></div>
+<div class="paragraph"><p>The following sections are currently available:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+About this book; Future additions
+</p>
+</li>
+<li>
+<p>
+<em>Workflow:</em> Think; Write; Stay productive
+</p>
+</li>
+<li>
+<p>
+<em>Documentation:</em> On documentation; Tutorials; User guide; Manual
+</p>
+</li>
+<li>
+<p>
+<em>Code:</em> Starting a project; Version control; Project structure; Code style; Best practices; Special processes
+</p>
+</li>
+<li>
+<p>
+<em>Tests:</em> On testing; Success typing analysis; Manual testing; Unit testing; Functional testing
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>Read a preview: <a href="/res/erlanger-preview.pdf">Special processes</a></p></div>
+<div class="paragraph"><p>The book is currently just shy of 100 pages. The final version
+of the book is planned to be between 200 and 250 pages.
+A print version of the book will be considered once the final
+version gets released. The printed book is <strong>not</strong> included
+in the price.</p></div>
+<div class="paragraph"><p>This is a self-published book. The base price is 50€. All proceeds
+will be used to allow me to work on open source full time.</p></div>
+<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
+<input type="hidden" name="cmd" value="_s-xclick">
+<input type="hidden" name="hosted_button_id" value="9M44HJCGX3GVN">
+<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
+<img alt="" border="0" src="https://www.paypalobjects.com/fr_FR/i/scr/pixel.gif" width="1" height="1">
+</form>
+<div class="paragraph"><p>You are more than welcome to pay extra by using this second button.
+It allows you to set the price you want. Make sure to set it to at least
+50€ to receive the book.</p></div>
+<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
+<input type="hidden" name="cmd" value="_s-xclick">
+<input type="hidden" name="hosted_button_id" value="BBW9TR9LBK8C2">
+<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
+<img alt="" border="0" src="https://www.paypalobjects.com/fr_FR/i/scr/pixel.gif" width="1" height="1">
+</form>
+<div class="paragraph"><p>Make sure to provide a valid email address.</p></div>
+<div class="paragraph"><p>There will be a <strong>delay</strong> between payment and sending of the book.
+This process is currently manual.</p></div>
+<div class="paragraph"><p>As the book is a pre-release, feedback is more than welcome. You can
+send your comments to erlanger@ this website.</p></div>
+<div class="paragraph"><p>The plan is to add about 20 pages every month until it is completed.
+You will receive updates to the book for free as soon as they are available.</p></div>
+<div class="paragraph"><p>Huge thanks for your interest in buying this book!</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/farwest-funded/index.html b/articles/farwest-funded/index.html new file mode 100644 index 00000000..1e0460d1 --- /dev/null +++ b/articles/farwest-funded/index.html @@ -0,0 +1,180 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Farwest got funded!</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Farwest got funded!</span></h1> + <p class="date"> + <span class="day">27</span> + <span class="month">Jun</span> + </p> +</header> + +<div class="paragraph"><p>This was a triumph! I’m making a note here: HUGE SUCCESS!!</p></div>
+<iframe frameborder="0" scrolling="no" height="400px" width"236px" seamless="seamless" src="https://api.bountysource.com/user/fundraisers/83/embed"></iframe>
+<div class="paragraph"><p>It’s hard to overstate my satisfaction. Thanks to everyone who
+made this possible.</p></div>
+<div class="paragraph"><p>If you have backed this fundraiser, and haven’t provided your
+personal details yet, please do so quickly so that your rewards
+can be sent!</p></div>
+<div class="paragraph"><p>I am hoping that we will be able to make good use of all that
+money. The details of the expenses will be published regularly
+on the <a href="https://github.com/extend/farwest/wiki/2013-Fundraiser">2013 Fundraiser wiki page</a>,
+giving you full disclosure as to how your money is used.</p></div>
+<div class="paragraph"><p>It will take a little time to get things started, we are in
+summer after all! We will however act quickly to make the
+prototype easy enough to use so that the paid UI work can
+begin. This is also when user contributions will be welcome.</p></div>
+<div class="paragraph"><p>You can see the <a href="https://github.com/extend/farwest/wiki/Roadmap">Roadmap</a>
+to get more information on the current plans. This document will
+get updated as time goes on so check again later to see if you
+can help!</p></div>
+<div class="paragraph"><p>Look at me: still talking when there’s open source to do!</p></div>
+<div class="paragraph"><p>Thanks again for all your support. I really appreciate it.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/index.html b/articles/index.html new file mode 100644 index 00000000..34af7442 --- /dev/null +++ b/articles/index.html @@ -0,0 +1,382 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Articles</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link 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in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents" class="two_col"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<h1 class="lined-header"><span>Articles</span></h1> + + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></h2> + <p class="date"> + <span class="day">02</span> + <span class="month">Sep</span> + </p> + </header> + + <p>An update to The Erlanger Playbook is now available! The Erlanger Playbook is a book about software development using Erlang. It currently covers all areas from the conception, design, the writing of code, documentation and tests. The book is still a work in progress. Future topics will include refactoring, debugging and tracing, benchmarking, releases, community management (for open source projects). This update fixes a number of things and adds two chapters: IOlists and Erlang building blocks.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></h2> + <p class="date"> + <span class="day">18</span> + <span class="month">Jun</span> + </p> + </header> + + <p>I am proud to announce the pre-release of The Erlanger Playbook. The Erlanger Playbook is a book about software development using Erlang. It currently covers all areas from the conception, design, the writing of code, documentation and tests. The book is still a work in progress. Future topics will include refactoring, debugging and tracing, benchmarking, releases, community management (for open source projects). The following sections are currently available: About this book; Future additions Workflow: Think; Write; Stay productive Documentation: On documentation; Tutorials; User guide; Manual Code: Starting a project; Version control; Project structure; Code style; Best practices; Special processes Tests: On testing; Success typing analysis; Manual testing; Unit testing; Functional testing Read a preview: Special processes The book is currently just shy of 100 pages.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/erlanger-playbook/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></h2> + <p class="date"> + <span class="day">06</span> + <span class="month">Mar</span> + </p> + </header> + + <p>Yesterday I pushed Websocket permessage-deflate to Cowboy master. I also pushed a change in the way the code validates UTF-8 data (required for text and close frames as per the spec). When looking into why the permessage-deflate tests in autobahntestsuite were taking such a long time, I found that autobahn is using an adaptation of the algorithm named <a href="http://bjoern.hoehrmann.de/utf-8/decoder/dfa/">Flexible and Economical UTF-8 Decoder</a>. This is the C99 implementation: // Copyright (c) 2008-2009 Bjoern Hoehrmann <[email protected]> // See http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/erlang-validate-utf8/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></h2> + <p class="date"> + <span class="day">05</span> + <span class="month">Sep</span> + </p> + </header> + + <p>Last week I read a great article on contributing to open source by Alvaro Videla. He makes many great points and I am in agreement with most of it. This made me want to properly explain my point of view with regard to open source and contributions. Unlike most open source evangelism articles I will not talk about ideals or any of that crap, but rather my personal feelings and experience.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/on-open-source/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></h2> + <p class="date"> + <span class="day">23</span> + <span class="month">Aug</span> + </p> + </header> + + <p>As I am away from home with little to do (some call this a vacation) I wanted to reflect a little on the story so far, or how I arrived to Erlang and got to where I am now. The raw personal experience. It’ll be an article that’s more about social aspect, communities and marketing a project than technical considerations. As a period piece, it will also allow me to reflect on the evolution of Erlang in recent years.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/the-story-so-far/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></h2> + <p class="date"> + <span class="day">20</span> + <span class="month">Aug</span> + </p> + </header> + + <p>Now that Cowboy 1.0 is out, I can spend some of my time thinking about Cowboy 2.0 that will be released soon after Erlang/OTP 18.0. This entry discusses the proposed changes to query string handling in Cowboy. Cowboy 2.0 will respond to user wishes by simplifying the interface of the cowboy_req module. Users want two things: less juggling with the Req variable, and more maps. Maps is the only dynamic key/value data structure in Erlang that we can match directly to extract values, allowing users to greatly simplify their code as they don’t need to call functions to do everything anymore.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/cowboy2-qs/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></h2> + <p class="date"> + <span class="day">07</span> + <span class="month">Jan</span> + </p> + </header> + + <p>I will now be regularly writing posts about project status, plans and hopes for the future. Before that though, there’s one important news to share. Until a year ago all development was financed through consulting and development services. This worked alright but too much time was spent doing things that didn’t benefit the open source projects. And that didn’t make me happy at all. Because I like being happy I stopped that for the most part and spent the year figuring things out, experimenting and discussing with people about it.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/january-2014-status/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></h2> + <p class="date"> + <span class="day">27</span> + <span class="month">Jun</span> + </p> + </header> + + <p>This was a triumph! I’m making a note here: HUGE SUCCESS!! It’s hard to overstate my satisfaction. Thanks to everyone who made this possible. If you have backed this fundraiser, and haven’t provided your personal details yet, please do so quickly so that your rewards can be sent! I am hoping that we will be able to make good use of all that money. The details of the expenses will be published regularly on the 2013 Fundraiser wiki page, giving you full disclosure as to how your money is used.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/farwest-funded/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></h2> + <p class="date"> + <span class="day">28</span> + <span class="month">May</span> + </p> + </header> + + <p>Building OTP releases has always been a difficult task. Tools like Reltool or Rebar have made this simpler, but it’s no panacea. This article will show you an alternative and hopefully much simpler solution. There is two steps to building a release. First you need to build the various OTP applications you want to include in the release. Once done, you need to create the release itself, by including the Erlang runtime system alongside the applications, a boot script to start the node and all its applications, and some configuration files.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/erlang.mk-and-relx/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></h2> + <p class="date"> + <span class="day">25</span> + <span class="month">Mar</span> + </p> + </header> + + <p>Today we will start the work on the intermediate module that will be used to run the code for the expressions found in our file’s body, replacing our interpreter. This is what we want to have when all the work is done: xerl -> tokens -> AST -> intermediate -> cerl Today we will perform this work only on the atomic integer expression however, so we will not build any module at the end.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></h2> + <p class="date"> + <span class="day">01</span> + <span class="month">Mar</span> + </p> + </header> + + <p>As promised we are adding an expression separator this time. This will be short and easy. In the tokenizer we only need to add a line recognizing the comma as a valid token. , : {token, {',', TokenLine}}. Then we need to change the following lines in the parser: exprs -> expr : ['$1']. exprs -> expr exprs : ['$1' | '$2']. And add a comma between the expressions on the second line: exprs -> expr : ['$1'].</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></h2> + <p class="date"> + <span class="day">18</span> + <span class="month">Feb</span> + </p> + </header> + + <p>I would like to share some experience and theories on Erlang scalability. This will be in the form of a series of hints, which may or may not be accompanied with explanations as to why things are this way, or how they improve or reduce the scalability of a system. I will try to do my best to avoid giving falsehoods, even if that means a few things won’t be explained.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/erlang-scalability/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></h2> + <p class="date"> + <span class="day">18</span> + <span class="month">Feb</span> + </p> + </header> + + <p>We will be adding atomic integer expressions to our language. These look as follow in Erlang: 42. And the result of this expression is of course 42. We will be running this expression at compile time, since we don’t have the means to run code at runtime yet. This will of course result in no module being compiled, but that’s OK, it will allow us to discuss a few important things we’ll have to plan for later on.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></h2> + <p class="date"> + <span class="day">03</span> + <span class="month">Feb</span> + </p> + </header> + + <p>Everything is an expression. This sentence carries profound meaning. We will invoke it many times over the course of these articles. If everything is an expression, then the language shouldn’t have any problem with me defining two modules in the same source file. mod first_module begin end mod second_module begin end Likewise, it shouldn’t have any problem with me defining a module inside another module. mod out_module begin mod in_module begin end end Of course, in the context of the Erlang VM, these two snippets are equivalent; there is nothing preventing you from calling the in_module module from any other module.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></h2> + <p class="date"> + <span class="day">30</span> + <span class="month">Jan</span> + </p> + </header> + + <p>Let’s build a programming language. I call it Xerl: eXtended ERLang. It’ll be an occasion for us to learn a few things, especially me. Unlike in Erlang, in this language, everything is an expression. This means that modules and functions are expression, and indeed that you can have more than one module per file. We are just starting, so let’s no go ahead of ourselves here. We’ll begin with writing the code allowing us to compile an empty module.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></h2> + <p class="date"> + <span class="day">14</span> + <span class="month">Nov</span> + </p> + </header> + + <p>Last week I was speaking at the London Erlang Factory Lite where I presented a live demonstration of building an FTP server using Ranch. As there was no slide, you should use this article as a reference instead. The goal of this article is to showcase how to use Ranch for writing a network protocol implementation, how Ranch gets out of the way to let you write the code that matters, and the common techniques used when writing servers.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/ranch-ftp/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> + <h2><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></h2> + <p class="date"> + <span class="day">17</span> + <span class="month">Oct</span> + </p> + </header> + + <p>Everyone knows Tic Tac Toe, right? Players choose either to be the Xs or the Os, then place their symbol on a 3x3 board one after another, trying to create a line of 3 of them. Writing an algorithm to check for victory sounds easy, right? It’s easily tested, considering there’s only 8 possible winning rows (3 horizontal, 3 vertical and 2 diagonal). In Erlang though, you probably wouldn’t want an algorithm.</p> + + <p style="text-align:right"> + <a class="read_more" href="http://ninenines.eu/articles/tictactoe/">Read More</a> + </p> + </article> + + + + + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/index.xml b/articles/index.xml new file mode 100644 index 00000000..81663a56 --- /dev/null +++ b/articles/index.xml @@ -0,0 +1,1919 @@ +<?xml version="1.0" encoding="utf-8" standalone="yes" ?> +<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"> + <channel> + <title>Articles on Nine Nines</title> + <link>http://ninenines.eu/articles/</link> + <description>Recent content in Articles on Nine Nines</description> + <generator>Hugo -- gohugo.io</generator> + <language>en-us</language> + <lastBuildDate>Wed, 02 Sep 2015 00:00:00 +0100</lastBuildDate> + <atom:link href="http://ninenines.eu/articles/index.xml" rel="self" type="application/rss+xml" /> + + <item> + <title>The Erlanger Playbook September 2015 Update</title> + <link>http://ninenines.eu/articles/erlanger-playbook-september-2015-update/</link> + <pubDate>Wed, 02 Sep 2015 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/erlanger-playbook-september-2015-update/</guid> + <description><div class="paragraph"><p>An update to The Erlanger Playbook is now available!</p></div>
+<div class="paragraph"><p>The Erlanger Playbook is a book about software development using
+Erlang. It currently covers all areas from the conception, design,
+the writing of code, documentation and tests.</p></div>
+<div class="paragraph"><p>The book is still a work in progress. Future topics will include
+refactoring, debugging and tracing, benchmarking, releases, community
+management (for open source projects).</p></div>
+<div class="paragraph"><p>This update fixes a number of things and adds two chapters: IOlists
+and Erlang building blocks.</p></div>
+<div class="paragraph"><p>Learn more about <a href="http://ninenines.eu/articles/erlanger-playbook">The Erlanger Playbook</a>!</p></div>
+<div class="paragraph"><p>This is a self-published ebook. The base price is 50€. All proceeds
+will be used to allow me to work on open source full time.</p></div>
+<div class="paragraph"><p>Thank you for helping me helping you help us all!</p></div>
+</description> + </item> + + <item> + <title>The Erlanger Playbook</title> + <link>http://ninenines.eu/articles/erlanger-playbook/</link> + <pubDate>Thu, 18 Jun 2015 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/erlanger-playbook/</guid> + <description><div class="paragraph"><p>I am proud to announce the pre-release of The Erlanger Playbook.</p></div>
+<div class="paragraph"><p>The Erlanger Playbook is a book about software development using
+Erlang. It currently covers all areas from the conception, design,
+the writing of code, documentation and tests.</p></div>
+<div class="paragraph"><p>The book is still a work in progress. Future topics will include
+refactoring, debugging and tracing, benchmarking, releases, community
+management (for open source projects).</p></div>
+<div class="paragraph"><p>The following sections are currently available:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+About this book; Future additions
+</p>
+</li>
+<li>
+<p>
+<em>Workflow:</em> Think; Write; Stay productive
+</p>
+</li>
+<li>
+<p>
+<em>Documentation:</em> On documentation; Tutorials; User guide; Manual
+</p>
+</li>
+<li>
+<p>
+<em>Code:</em> Starting a project; Version control; Project structure; Code style; Best practices; Special processes
+</p>
+</li>
+<li>
+<p>
+<em>Tests:</em> On testing; Success typing analysis; Manual testing; Unit testing; Functional testing
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>Read a preview: <a href="http://ninenines.eu/res/erlanger-preview.pdf">Special processes</a></p></div>
+<div class="paragraph"><p>The book is currently just shy of 100 pages. The final version
+of the book is planned to be between 200 and 250 pages.
+A print version of the book will be considered once the final
+version gets released. The printed book is <strong>not</strong> included
+in the price.</p></div>
+<div class="paragraph"><p>This is a self-published book. The base price is 50€. All proceeds
+will be used to allow me to work on open source full time.</p></div>
+<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
+<input type="hidden" name="cmd" value="_s-xclick">
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+</description> + </item> + + <item> + <title>Validating UTF-8 binaries with Erlang</title> + <link>http://ninenines.eu/articles/erlang-validate-utf8/</link> + <pubDate>Fri, 06 Mar 2015 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/erlang-validate-utf8/</guid> + <description><div class="paragraph"><p>Yesterday I pushed Websocket permessage-deflate to
+Cowboy master. I also pushed
+<a href="https://github.com/ninenines/cowlib/commit/7e4983b70ddf8cedb967e36fba6a600731bdad5d">a
+change in the way the code validates UTF-8 data</a>
+(required for text and close frames as per the spec).</p></div>
+<div class="paragraph"><p>When looking into why the permessage-deflate tests
+in autobahntestsuite were taking such a long time, I
+found that autobahn is using an adaptation of the
+algorithm named &lt;a href="http://bjoern.hoehrmann.de/utf-8/decoder/dfa/"&gt;Flexible
+and Economical UTF-8 Decoder&lt;/a&gt;. This is the C99
+implementation:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-style: italic"><span style="color: #9A1900">// Copyright (c) 2008-2009 Bjoern Hoehrmann &lt;[email protected]&gt;</span></span>
+<span style="font-style: italic"><span style="color: #9A1900">// See http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.</span></span>
+
+<span style="font-weight: bold"><span style="color: #000080">#define</span></span> UTF8_ACCEPT <span style="color: #993399">0</span>
+<span style="font-weight: bold"><span style="color: #000080">#define</span></span> UTF8_REJECT <span style="color: #993399">1</span>
+
+<span style="font-weight: bold"><span style="color: #0000FF">static</span></span> <span style="font-weight: bold"><span style="color: #0000FF">const</span></span> <span style="color: #008080">uint8_t</span> utf8d<span style="color: #990000">[]</span> <span style="color: #990000">=</span> <span style="color: #FF0000">{</span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 00..1f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 20..3f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 40..5f</span></span>
+ <span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 60..7f</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span><span style="color: #993399">9</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// 80..9f</span></span>
+ <span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span><span style="color: #993399">7</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// a0..bf</span></span>
+ <span style="color: #993399">8</span><span style="color: #990000">,</span><span style="color: #993399">8</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// c0..df</span></span>
+ <span style="color: #993399">0xa</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x4</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// e0..ef</span></span>
+ <span style="color: #993399">0xb</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x5</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// f0..ff</span></span>
+ <span style="color: #993399">0x0</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x2</span><span style="color: #990000">,</span><span style="color: #993399">0x3</span><span style="color: #990000">,</span><span style="color: #993399">0x5</span><span style="color: #990000">,</span><span style="color: #993399">0x8</span><span style="color: #990000">,</span><span style="color: #993399">0x7</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x4</span><span style="color: #990000">,</span><span style="color: #993399">0x6</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span><span style="color: #993399">0x1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s0..s0</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">0</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s1..s2</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s3..s4</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">2</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s5..s6</span></span>
+ <span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">3</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span><span style="color: #993399">1</span><span style="color: #990000">,</span> <span style="font-style: italic"><span style="color: #9A1900">// s7..s8</span></span>
+<span style="color: #FF0000">}</span><span style="color: #990000">;</span>
+
+uint32_t inline
+<span style="font-weight: bold"><span style="color: #000000">decode</span></span><span style="color: #990000">(</span>uint32_t<span style="color: #990000">*</span> state<span style="color: #990000">,</span> uint32_t<span style="color: #990000">*</span> codep<span style="color: #990000">,</span> <span style="color: #008080">uint32_t</span> byte<span style="color: #990000">)</span> <span style="color: #FF0000">{</span>
+ <span style="color: #008080">uint32_t</span> type <span style="color: #990000">=</span> utf8d<span style="color: #990000">[</span>byte<span style="color: #990000">];</span>
+
+ <span style="color: #990000">*</span>codep <span style="color: #990000">=</span> <span style="color: #990000">(*</span>state <span style="color: #990000">!=</span> UTF8_ACCEPT<span style="color: #990000">)</span> <span style="color: #990000">?</span>
+ <span style="color: #990000">(</span>byte <span style="color: #990000">&amp;</span> <span style="color: #993399">0x3fu</span><span style="color: #990000">)</span> <span style="color: #990000">|</span> <span style="color: #990000">(*</span>codep <span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">6</span><span style="color: #990000">)</span> <span style="color: #990000">:</span>
+ <span style="color: #990000">(</span><span style="color: #993399">0xff</span> <span style="color: #990000">&gt;&gt;</span> type<span style="color: #990000">)</span> <span style="color: #990000">&amp;</span> <span style="color: #990000">(</span>byte<span style="color: #990000">);</span>
+
+ <span style="color: #990000">*</span>state <span style="color: #990000">=</span> utf8d<span style="color: #990000">[</span><span style="color: #993399">256</span> <span style="color: #990000">+</span> <span style="color: #990000">*</span>state<span style="color: #990000">*</span><span style="color: #993399">16</span> <span style="color: #990000">+</span> type<span style="color: #990000">];</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">return</span></span> <span style="color: #990000">*</span>state<span style="color: #990000">;</span>
+<span style="color: #FF0000">}</span></tt></pre></div></div>
+<div class="paragraph"><p>And this is the Erlang implementation I came up with:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-style: italic"><span style="color: #9A1900">%% This function returns 0 on success, 1 on error, and 2..8 on incomplete data.</span></span>
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;&gt;&gt;</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span> <span style="color: #009900">State</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">128</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">144</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">144</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">144</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">144</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">8</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">128</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">144</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">192</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">192</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">4</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">192</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">192</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">160</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">192</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">194</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">224</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">224</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">4</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">225</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">237</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">237</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">5</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">238</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">239</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">240</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">6</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">241</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">242</span>; <span style="color: #009900">C</span> <span style="color: #990000">=:=</span> <span style="color: #993399">243</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">7</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">244</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">8</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">_</span>, <span style="color: #990000">_</span>) <span style="color: #990000">-&gt;</span> <span style="color: #993399">1</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Does it look similar to you? So how did we get there?</p></div>
+<div class="paragraph"><p>I started with a naive implementation of the original. First, we
+don&#8217;t need the codepoint calculated and extracted for our validation
+function. We just want to know the data is valid, so we only need to
+calculate the next state. Then, the only thing we needed to be careful
+about was that tuples are 1-based, and that we need to stop processing
+the binary when we get the state 1 or when the binary is empty.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;&gt;&gt;</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span> <span style="color: #009900">State</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">_</span>, <span style="color: #993399">1</span>) <span style="color: #990000">-&gt;</span> <span style="color: #993399">1</span>;
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">257</span> <span style="color: #990000">+</span> <span style="color: #009900">State</span> <span style="color: #990000">*</span> <span style="color: #993399">16</span> <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">1</span> <span style="color: #990000">+</span> <span style="color: #009900">C</span>, <span style="font-weight: bold"><span style="color: #000080">?UTF8D</span></span>), <span style="font-weight: bold"><span style="color: #000080">?UTF8D</span></span>))<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The macro <code>?UTF8D</code> is the tuple equivalent of the C array
+in the original code.</p></div>
+<div class="paragraph"><p>Compared to our previous algorithm, this performed about the same.
+In some situations a little faster, in some a little slower. In other words,
+not good enough. But because this new algorithm allows us to avoid a binary
+concatenation this warranted looking further.</p></div>
+<div class="paragraph"><p>It was time to step into crazy land.</p></div>
+<div class="paragraph"><p>Erlang is very good at pattern matching, even more so than doing some
+arithmetic coupled by fetching elements from a tuple. So I decided I was
+going to write all possible clauses for all combinations of <code>C</code>
+and <code>State</code>. And by write I mean generate.</p></div>
+<div class="paragraph"><p>So I opened my Erlang shell, defined the variable <code>D</code> to be
+the tuple <code>?UTF8D</code> with its 400 elements, and then ran the
+following expression (after a bit of trial and error):</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">16</span><span style="color: #990000">&gt;</span> <span style="font-weight: bold"><span style="color: #000000">file:write_file</span></span>(<span style="color: #FF0000">"out.txt"</span>,
+ [<span style="font-weight: bold"><span style="color: #000000">io_lib:format</span></span>(<span style="color: #FF0000">"validate_utf8(&lt;&lt; ~p, Rest/bits &gt;&gt;, ~p) -&gt; ~p;~n"</span>,
+ [<span style="color: #009900">C</span>, <span style="color: #009900">S</span>, <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">257</span> <span style="color: #990000">+</span> <span style="color: #009900">S</span> <span style="color: #990000">*</span> <span style="color: #993399">16</span> <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000080">element</span></span>(<span style="color: #993399">1</span> <span style="color: #990000">+</span> <span style="color: #009900">C</span>, <span style="color: #009900">D</span>), <span style="color: #009900">D</span>)])
+ || <span style="color: #009900">C</span> <span style="color: #990000">&lt;-</span> <span style="font-weight: bold"><span style="color: #000000">lists:seq</span></span>(<span style="color: #993399">0</span>,<span style="color: #993399">255</span>), <span style="color: #009900">S</span> <span style="color: #990000">&lt;-</span> <span style="font-weight: bold"><span style="color: #000000">lists:seq</span></span>(<span style="color: #993399">0</span>,<span style="color: #993399">8</span>)])<span style="color: #990000">.</span>
+<span style="color: #FF6600">ok</span></tt></pre></div></div>
+<div class="paragraph"><p>The result is a 2304 lines long file, containing 2304 clauses.
+People who pay attention to what I say on Twitter will remember
+I said something around 3000 clauses, but that was just me not
+using the right number of states in my estimate.</p></div>
+<div class="paragraph"><p>There was a little more work to be done on this generated
+code that I did using regular expressions. We need to recurse
+when the resulting state is not 1. We also need to stop when
+the binary is empty, making it the 2305th clause.</p></div>
+<div class="paragraph"><p>Still, 2305 is a lot. But hey, the code did work, and faster
+than the previous implementation too! But hey, perhaps I could
+find a way to reduce its size.</p></div>
+<div class="paragraph"><p>Removing all the clauses that return 1 and putting a catch-all
+clause at the end instead reduced the number to about 500, and
+showed that many clauses were similar:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">0</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">1</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">2</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">3</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">4</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">5</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">6</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">7</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);</tt></pre></div></div>
+<div class="paragraph"><p>But also:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">5</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">6</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">157</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">5</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">6</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #993399">158</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);</tt></pre></div></div>
+<div class="paragraph"><p>Patterns, my favorites!</p></div>
+<div class="paragraph"><p>A little more time was spent to edit the 500 or so clauses into
+smaller equivalents, testing that performance was not impacted, and
+comitting the result.</p></div>
+<div class="paragraph"><p>The patterns above can be found here in the resulting function:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">0</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">128</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="color: #990000">...</span>
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">2</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">0</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">3</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">5</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">2</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">6</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #990000">&lt;&lt;</span> <span style="color: #009900">C</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span> <span style="color: #990000">&gt;&gt;</span>, <span style="color: #993399">7</span>) <span style="font-weight: bold"><span style="color: #0000FF">when</span></span> <span style="color: #009900">C</span> <span style="color: #990000">&gt;=</span> <span style="color: #993399">144</span>, <span style="color: #009900">C</span> <span style="color: #990000">&lt;</span> <span style="color: #993399">160</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">validate_utf8</span></span>(<span style="color: #009900">Rest</span>, <span style="color: #993399">3</span>);
+<span style="color: #990000">...</span></tt></pre></div></div>
+<div class="paragraph"><p>I hope you enjoyed this post.</p></div>
+</description> + </item> + + <item> + <title>On open source</title> + <link>http://ninenines.eu/articles/on-open-source/</link> + <pubDate>Fri, 05 Sep 2014 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/on-open-source/</guid> + <description><div class="paragraph"><p>Last week I read a great article
+<a href="http://videlalvaro.github.io/2014/08/on-contributing-to-opensource.html">on
+contributing to open source</a> by Alvaro Videla. He makes
+many great points and I am in agreement with most of it.
+This made me want to properly explain my point of view with
+regard to open source and contributions. Unlike most open
+source evangelism articles I will not talk about ideals or
+any of that crap, but rather my personal feelings and
+experience.</p></div>
+<div class="paragraph"><p>I have been doing open source work for quite some time.
+My very first open source project was a graphics driver
+for (the very early version of) the PCSX2 emulator. That
+was more than ten years ago, and there
+<a href="http://ngemu.com/threads/gstaris-0-6.30469/">isn&#8217;t
+much left to look at today</a>. This was followed by a
+<a href="https://github.com/extend/wee">PHP framework</a>
+(started long before Zend Framework was even a thing) and
+a few other small projects. None of them really took off.
+It&#8217;s alright, that&#8217;s pretty much the fate of most open
+source projects. You spend a lot of work and sweat and
+get very little in return from others.</p></div>
+<div class="paragraph"><p>This sounds harsh but this is the reality of all open
+source projects. If you are thinking of building a project
+and releasing it as open source, you should be prepared
+for that. This is how most of your projects will feel like.
+Don&#8217;t release a project as open source thinking everyone
+will pat you on the back and cheer, this won&#8217;t happen. In
+fact if your project is a too small improvement over existing
+software, what many people will do is say you have NIH
+syndrome, regardless of the improvement you bring. So you
+need not to rely on other people in order to get your
+enjoyment out of building open source software.</p></div>
+<div class="paragraph"><p>In my case I get enjoyment from thinking about problems
+that need solving. Often times the problems are already
+solved, but nevermind that, I still think about them and
+sometimes come up with something I feel is better and then
+write code for it. Writing code is also fun, but not as
+fun as using my brain to imagine solutions.</p></div>
+<div class="paragraph"><p>You don&#8217;t need thousands of users to do that. So are
+users worthless to me then? No, of course not. In fact
+they are an important component: they bring me problems
+that need solving. So users are very important to me.
+But that&#8217;s not the only reason.</p></div>
+<div class="paragraph"><p>I got lucky that the Cowboy project became popular.
+And seeing it be this popular, and some of my other projects
+also do quite well, made me believe I could perhaps work
+full time on open source. If I can work full time then
+I can produce better software. What I had one hour to
+work on before I can now spend a day on, and experiment
+until I am satisfied. This is very useful because that
+means I can get it almost right from the beginning, and
+avoid the million API breaking changes that occured
+before Cowboy 1.0 was released.</p></div>
+<div class="paragraph"><p>To be able to work full time on open source however,
+I need money. This is a largely unspoken topic of open
+source work. The work is never free. You can download the
+product for free, but someone has to pay for the work
+itself. Life is unfortunately not free.</p></div>
+<div class="paragraph"><p>Large projects and some lucky people have their work
+sponsored by their employers. Everyone else has to deal
+with it differently. In my case I was sponsored for a
+while by the <a href="http://leo-project.net/leofs/">LeoFS</a>
+project, but that ended. I also had the Farwest fundraiser,
+which was a success, although the project stalled after that.
+(Fear not, as Farwest will make a comeback as a conglomerate
+of Web development projects in the future.) After that I set
+up the <a href="http://ninenines.eu/support/">sponsoring scheme</a>,
+which I can proudly say today brings in enough money to
+cover my food and shelter. Great!</p></div>
+<div class="paragraph"><p>This is a start, but it&#8217;s of course not enough. Life
+is a little more than food and shelter, and so I am still
+looking for sponsors. This is not a very glorious experience,
+as I am essentially looking for scraps that companies can
+throw away. Still, if a handful more companies were doing
+that, not only would I be able to live comfortably, but I
+would also be able to stop worrying about the future as I
+could put money on the side for when it gets rough.</p></div>
+<div class="paragraph"><p>A few companies giving me some scrap money so I could
+live and work independently is by far the most important
+thing anyone can do to help my projects, including Cowboy.
+Yes, they&#8217;re even more important than code contributions,
+bug reports and feedback. Because this money gives me the
+time I need to handle the code contributions, bug reports
+and feedback.</p></div>
+<div class="paragraph"><p>If Cowboy or another project is a large part of your
+product or infrastructure, then the best thing you can do
+is become a sponsor. The second best is opening tickets
+and/or providing feedback. The third best is providing
+good code contributions.</p></div>
+<div class="paragraph"><p>I will not expand on the feedback part. Feedback is
+very important, and even just a high five or a retweet
+is already good feedback. It&#8217;s not very complicated.</p></div>
+<div class="paragraph"><p>I want to expand a little on code contributions
+however. Not long ago I ran across the term "patch bomb"
+which means dropping patches and expecting the project
+maintainers to merge them and maintain them. I receive
+a lot of patches, and often have to refuse them. Causes
+for refusal vary. Some patches only benefit the people
+who submitted them (or a very small number of people).
+Some patches are not refined enough to be included.
+Others are out of scope of the project. These are some
+of the reasons why I refuse patches. Having limited
+time and resources, I have to focus my efforts on the
+code used by the larger number of users. I have to
+prioritize patches from submitters who are reactive
+and address the issues pointed out. And I have to plainly
+refuse other patches.</p></div>
+<div class="paragraph"><p>I believe this wraps up my thoughts on open source.
+Overall I had a great experience, the Erlang community
+being nice and understanding of the issues at hand in
+general. And if the money problem could be solved soon,
+then I would be one of the luckiest and happiest open
+source developer on Earth.</p></div>
+<div class="paragraph"><p>Think about it the next time you see a donation button
+or a request for funds or sponsoring. You can considerably
+improve an open source developer&#8217;s life with very little
+of your company&#8217;s money.</p></div>
+</description> + </item> + + <item> + <title>The story so far</title> + <link>http://ninenines.eu/articles/the-story-so-far/</link> + <pubDate>Sat, 23 Aug 2014 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/the-story-so-far/</guid> + <description><div class="paragraph"><p>As I am away from home with little to do (some call this
+a vacation) I wanted to reflect a little on the story so far,
+or how I arrived to Erlang and got to where I am now. The
+raw personal experience. It&#8217;ll be an article that&#8217;s more
+about social aspect, communities and marketing a project than
+technical considerations. As a period piece, it will also
+allow me to reflect on the evolution of Erlang in recent
+years.</p></div>
+<div class="paragraph"><p>Once upon a time-- Okay this isn&#8217;t a fairy tale. The story
+begins with a short chapter in 2010. The year 2010 started
+with a fairly major event in my life: the US servers for the
+online game I stopped playing a few months before, but was
+still involved with through its community, were closing. OMG!
+Someone found a way to log packets and started working on a
+private server; meanwhile the JP servers were still up. And
+that&#8217;s pretty much it.</p></div>
+<div class="paragraph"><p>Fast forward a few months and it became pretty clear that
+the private server was going nowhere considering all the drama
+surrounding it-- which is actually not unusual, but it was
+more entertaining than average and the technical abilities of
+people running the project were obviously lacking so I decided
+to obtain those logged packets and look at things myself. I
+didn&#8217;t want to do a private server yet, I only wanted to take
+a peek to see how things worked, and perhaps organize some
+effort to document the protocol.</p></div>
+<div class="paragraph"><p>There was 10GB of logs. I didn&#8217;t have an easy to use
+language to analyze them, and hex editors wouldn&#8217;t cut it for
+most purposes, so I had to look elsewhere. This was a good
+opportunity to start learning this PHP killer I read about
+before, which also happens to feature syntax for matching
+binaries, called Erlang. To be perfectly honest I wouldn&#8217;t
+have touched the logs if I didn&#8217;t have the added motivation
+to play with and learn a new language.</p></div>
+<div class="paragraph"><p>At the time it was pretty hard to learn Erlang. In my
+experience there was Joe&#8217;s book (which I always recommend
+first as I believe it is the best to learn the Erlang side
+of things; but falls a little short on OTP), and there was
+about 5 chapters of LYSE. There were a couple other books
+I never managed to get into (sorry guys), and there was also
+a few interesting blogs, some of which I can&#8217;t find anymore.
+Finally the #erlang IRC community was there but I was strictly
+lurking at the time.</p></div>
+<div class="paragraph"><p>What a difference compared to 4 years later! (That&#8217;s
+today, by the way!) Now we have more books than I can
+remember, tons of articles covering various aspects of the
+language and platform, many targeting beginners but a good
+number of them also about advanced topics. We even have a
+free online book, LYSE, with more than 30 chapters covering
+pretty much everything. Needless to say I never finished
+reading LYSE as it got written slower than I learnt.</p></div>
+<div class="paragraph"><p>Back to 2010. I wrote a parser for the logs, and
+aggregated those results into one CSV file per packet type
+so I could open them in Gnumeric and aggregate some more,
+but manually this time, and draw conclusions on the packet
+structures. That was pretty easy. Even for a beginner.
+Anyone can go from zero to that level in a day or two.
+Then, having mastered binary pattern matching, I wanted
+to learn some more Erlang, by making this aggregation
+faster. What I had done before worked, but I wasn&#8217;t going
+to wait forever to process everything sequentially. So I
+looked and found a project called <code>plists</code> (still exists,
+but not maintained AFAIK). I downloaded that project and
+replaced my <code>lists:</code> calls to <code>plists:</code>.
+Boom. In just a few minutes all logs were processed, and
+I had learnt something new.</p></div>
+<div class="paragraph"><p>It is particularly interesting to note that the lack of
+a package manager or index never bothered me. Neither before
+nor after learning Erlang. My experience with package
+managers was mostly related to Ubuntu, a little Perl and
+Python, and PHP&#8217;s Pear. Let&#8217;s just stay polite and say it
+was always a terrible experience. So searching on the Web
+didn&#8217;t feel awkward, because even if I used a tool or
+website I would have ended up doing a search or two anyway.
+This is in contrast to the package index feature in
+<a href="https://github.com/ninenines/erlang.mk">Erlang.mk</a>,
+which is meant to simplify specifying dependencies more
+than anything: <code>DEPS = cowboy</code>. It does not
+attempt to solve any other problem, and will only attempt
+to solve one extra problem in the near future, which is
+the discovery of packages. So expect some kind of website
+listing packages soon enough.</p></div>
+<div class="paragraph"><p>I want to use this parenthese to also point out that at
+the time there was a very small number of projects out there,
+at least compared to today. While you sometimes hear people
+complain about lack of certain libraries, it is so much
+better now than it was before! The situation improves very
+quickly, so much that it&#8217;s not going to be that big an issue
+soon enough.</p></div>
+<div class="paragraph"><p>Wanting to know more about that game&#8217;s protocol, in the
+year 2010, I ended up starting to write more Erlang code to
+simulate a server and use the server to query the client and
+see what was happening, documenting the packets and so on.
+This eventually lead to a larger project implementing more
+and more until people got their hopes up for a revival of
+the game, all the while the now competing original server
+project died in a stream of drama and technical incompetence.
+Of course, I ended up doing what any good Internet citizen
+would do, I crushed people&#8217;s hopes, but that&#8217;s not important
+to our story. The important part is that before giving up
+on this project, I not only learnt a good deal of Erlang
+and a little deal of OTP (which I did not touch until 6
+months after I started with Erlang; see the paragraph
+about learning material above), but I also had an intriguing
+idea pop into my mind for what would become my greatest
+success yet.</p></div>
+<div class="paragraph"><p>The giving up part was not easy. Having had financial
+difficulties all year 2010 and part of 2009, I resolved
+to travel back to Paris to try and make it. I ended up
+sleeping in offices for 6 months, being hosted by a shady
+person, and hearing my fair share of stories about
+the dark side of business. While there I also worked for
+another company with someone who would end up becoming
+another high profile Erlang developer. The situation
+slowly improved, I started taking part in the #erlang
+IRC discussions, giving up my status of lurker and, a
+few months into 2011, started working on the Apache killer
+project: Cowboy.</p></div>
+<div class="paragraph"><p>This is the part where I probably should get accused of
+racism and other fun things, but I never did. And I think
+that speaks lots about the Erlang community. In all my time
+writing Erlang code, I can count the number of conflicts I
+had with other people on a single hand. This is the nicest
+programming community I have ever seen, by far. And the
+humblest too. The Erlang community feels like Japan. And
+I love Japan. So I love the Erlang community. I can&#8217;t say
+this enough. This is something that stayed true for all
+my time using Erlang, and despite the rise of alternative
+languages that are not Japan the Erlang community has
+remained very Japan.</p></div>
+<div class="paragraph"><p>The first published version of Cowboy was written in
+two weeks. A little before those two weeks, during, and
+a while after, pretty much everything I said on the
+Internets was that Cowboy was going to be the greatest
+HTTP server ever, that the other servers were problematic
+(and just to be clear, Yaws was rarely if ever mentioned,
+due to being in a perceived different league of "full
+featured servers" while Cowboy was a "lightweight server"),
+and that Cowboy will be the best replacement to a Mochiweb
+or Misultin application. This, alongside a lot of time
+spent on IRC telling people to use Cowboy when they were
+asking for an HTTP server to use, probably made me sound
+very annoying. But it worked, and Cowboy started getting
+its first users, despite being only a few weeks old. Of
+course, as soon as I got my very first user, I started
+claiming Cowboy had "a lot of users".</p></div>
+<div class="paragraph"><p>Looking back today I would definitely find myself annoying,
+this wasn&#8217;t just an idle comment there. For about a year,
+maybe a little more, all I ever said was that Cowboy was
+the best. This probably made me a little dumber in the
+process (as if I wasn&#8217;t enough! I know). Being French, I
+sometimes would also say things quite abruptly. To stay
+polite, I probably sounded like an asshole. I learnt to
+stop being so French over time thankfully.</p></div>
+<div class="paragraph"><p>I think what was most important to Cowboy at the time,
+was three things. First, it felt fresh. It was new, had new
+ideas, tried to do things differently and followed "new" old
+best practices (the OTP way-- which was simply too obscure
+for most people at the time). Second, it had me spending
+all my time telling people to use it whenever they were
+looking for an HTTP server. Third, it had me helping people
+get started with it and guide them all the steps of the way.
+Mostly because it didn&#8217;t have a very good documentation, but
+still, hand holding does wonders.</p></div>
+<div class="paragraph"><p>To be able to help people every time they had a problem,
+I did not spend all my days reading IRC. Instead I simply
+made sure to be notified when someone said <code>cowboy</code>.
+The same way many people subscribe to alerts when their
+company is mentioned in the news. Nothing fancy.</p></div>
+<div class="paragraph"><p>Time went on, Cowboy grew, or as some like to say,
+completely destroyed the competition, and many people
+eventually moved from Mochiweb and Misultin to Cowboy.
+And then Roberto Ostinelli stopped Misultin development
+and told everyone to move to Cowboy. This is the most
+humble and selfless act I have ever seen in the programming
+sphere, and I only have one thing to say about it: GG.
+Thanks for the fish. He left me with the tasks of improving
+Cowboy examples, documentation and strongly believed that
+the Misultin interface was more user friendly out of all
+the servers. So I added many examples, as many lines of
+documentation as we have of code, and strongly believe
+that Cowboy 2.0 will be the most user friendly interface
+out of all servers. But only time will tell.</p></div>
+<div class="paragraph"><p>With the rise of the project and the rise in the number
+of users, my previous strategy (completely incidental, by
+the way, and definitely not a well thought out plan to
+become popular) stopped working. It was taking me too much
+time. The important aspects slowly drifted. If I wanted to
+support more users, I would have to spend less time with
+each individual user. This was actually a hard problem.
+You basically have to make people understand they can&#8217;t
+just come to you directly when they have a problem, they
+have to follow proper channels. It becomes less personal,
+and might be felt like you don&#8217;t care about them anymore.
+You have to hurt some people&#8217;s feelings at this point. It
+is quite unfortunate, and also quite difficult to do. There
+is some unwritten rule that says early adopters deserve
+more, but in the real world it never works like this. So
+I probably hurt some people&#8217;s feelings at some point. But
+that&#8217;s okay. Because even if you make sure to be as nice
+as possible when you tell people to go through proper
+channels from now on, some people will still get offended.
+There&#8217;s nothing you can do about it.</p></div>
+<div class="paragraph"><p>From that point onward the important points about the
+project was getting the documentation done, making sure
+people knew about the proper channels to get help and
+report issues, etc. Basically making myself less needed.
+This is quite a contrast with the first days, but I believe
+Cowboy made that transition successfully.</p></div>
+<div class="paragraph"><p>Not only did I win time by not having to hold hands with
+everyone all the time (not that I didn&#8217;t like it, but you
+know, the sweat), but I also won time thanks to the increased
+project popularity. Indeed, the more users you have, the more
+annoying guys there are to tell people to use your project
+and that it&#8217;s the best and everything. Which is great. At
+least, it&#8217;s great if you don&#8217;t pay too much attention to it.
+Sometimes people will give an advice that is, in your opinion,
+a bad advice. And that&#8217;s okay. Don&#8217;t intervene every time
+someone gives a bad advice, learn to let it go. People will
+figure it out. You learn by making mistakes, after all. Use
+this extra time to make sure other people don&#8217;t end up
+giving the same bad advice instead. Fix the code or the
+documentation that led to this mistake. Slowly improve the
+project and make sure it doesn&#8217;t happen again.</p></div>
+<div class="paragraph"><p>This is my story. So far, anyway.</p></div>
+</description> + </item> + + <item> + <title>Cowboy 2.0 and query strings</title> + <link>http://ninenines.eu/articles/cowboy2-qs/</link> + <pubDate>Wed, 20 Aug 2014 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/cowboy2-qs/</guid> + <description><div class="paragraph"><p>Now that Cowboy 1.0 is out, I can spend some of my time thinking
+about Cowboy 2.0 that will be released soon after Erlang/OTP 18.0.
+This entry discusses the proposed changes to query string handling
+in Cowboy.</p></div>
+<div class="paragraph"><p>Cowboy 2.0 will respond to user wishes by simplifying the interface
+of the <code>cowboy_req</code> module. Users want two things: less
+juggling with the Req variable, and more maps. Maps is the only
+dynamic key/value data structure in Erlang that we can match directly
+to extract values, allowing users to greatly simplify their code as
+they don&#8217;t need to call functions to do everything anymore.</p></div>
+<div class="paragraph"><p>Query strings are a good candidate for maps. It&#8217;s a list of
+key/values, so it&#8217;s pretty obvious we can win a lot by using maps.
+However query strings have one difference with maps: they can have
+duplicate keys.</p></div>
+<div class="paragraph"><p>How are we expected to handle duplicate keys? There&#8217;s no standard
+behavior. It&#8217;s up to applications. And looking at what is done in
+the wild, there&#8217;s no de facto standard either. While some ignore
+duplicate keys (keeping the first or the last they find), others
+require duplicate keys to end with <code>[]</code> to automatically
+put the values in a list, or even worse, languages like PHP even
+allow you to do things like <code>key[something][other]</code> and
+create a deep structure for it. Finally some allow any key to have
+duplicates and just gives you lists of key/values.</p></div>
+<div class="paragraph"><p>Cowboy so far had functions to retrieve query string values one
+value at a time, and if there were duplicates it would return the
+first it finds. It also has a function returning the entire list
+with all duplicates, allowing you to filter it to get all of them,
+and another function that returns the raw query string.</p></div>
+<div class="paragraph"><p>What are duplicates used for? Not that many things actually.</p></div>
+<div class="paragraph"><p>One use of duplicate keys is with HTML forms. It is common practice
+to give all related checkboxes the same name so you get a list of
+what&#8217;s been checked. When nothing is checked, nothing is sent at all,
+the key is not in the list.</p></div>
+<div class="paragraph"><p>Another use of duplicate keys is when generating forms. A good
+example of that would be a form that allows uploading any number
+of files. When you add a file, client-side code adds another field
+to the form. Repeat up to a certain limit.</p></div>
+<div class="paragraph"><p>And that&#8217;s about it. Of note is that HTML radio elements share
+the same name too, but only one key/value is sent, so they are not
+relevant here.</p></div>
+<div class="paragraph"><p>Normally this would be the part where I tell you how we solve
+this elegantly. But I had doubts. Why? Because there&#8217;s no good
+solutions to solving only this particular problem.</p></div>
+<div class="paragraph"><p>I then stopped thinking about duplicate keys for a minute and
+started to think about the larger problem.</p></div>
+<div class="paragraph"><p>Query strings are input data. They take a particular form,
+and may be sent as part of the URI or as part of the request
+body. We have other kinds of input data. We have headers and
+cookies and the request body in various forms. We also have
+path segments in URIs.</p></div>
+<div class="paragraph"><p>What do you do with input data? Well you use it to do
+something. But there is one thing that you almost always do
+(and if you don&#8217;t, you really should): you validate it and
+you map it into Erlang terms.</p></div>
+<div class="paragraph"><p>Cowboy left the user take care of validation and conversion
+into Erlang terms so far. Rather, it left the user take care
+of it everywhere except one place. Guess where? That&#8217;s right,
+bindings.</p></div>
+<div class="paragraph"><p>If you define routes with bindings then you have the option
+to provide constraints. Constraints can be used to do two things:
+validate the data and convert it in a more appropriate term. For
+example if you use the <code>int</code> constraint, Cowboy will
+make sure the binding is an integer, and will replace the value
+with the integer representation so that you can use it directly.
+In this particular case it not only routes the URI, but also
+validates and converts the bindings directly.</p></div>
+<div class="paragraph"><p>This is very relevant in the case of our duplicate keys,
+because if we have a list with duplicates of a key, chances
+are we want to convert that into a list of Erlang terms, and
+also make sure that all the elements in this list are expected.</p></div>
+<div class="paragraph"><p>The answer to this particular problem is simple. We need a
+function that will parse the query string and apply constraints.
+But this is not all, there is one other problem to be solved.</p></div>
+<div class="paragraph"><p>The other problem is that for the user some keys are mandatory
+and some are optional. Optional keys include the ones that
+correspond to HTML checkboxes: if the key for one or more
+checkbox is missing from the query string, we still want to
+have an empty list in our map so we can easily match. Matching
+maps is great, but not so much when values might be missing,
+so we have to normalize this data a little.</p></div>
+<div class="paragraph"><p>This problem is solved by allowing a default value. If the
+key is missing and a default exists, set it. If no default
+exists, then the key was mandatory and we want to crash.</p></div>
+<div class="paragraph"><p>I therefore make a proposal for changing the query string
+interface to three functions.</p></div>
+<div class="paragraph"><p>The first function already exists, it is <code>cowboy_req:qs(Req)</code>
+and it returns only the query string binary. No more Req returned.</p></div>
+<div class="paragraph"><p>The second function is a renaming of <code>cowboy_req:qs_vals(Req)</code>
+to something more explicit: <code>cowboy_req:parse_qs(Req)</code>.
+The new name implies that a parsing operation is done. It was implicit
+and cached before. It will be explicit and not cached anymore now.
+Again, no more Req returned.</p></div>
+<div class="paragraph"><p>The third function is the one I mentioned above. I think
+the interface <code>cowboy_req:match_qs(Req, Fields)</code> is
+most appropriate. It returns a normalized map that is the same
+regardless of optional fields being provided with the request,
+allowing for easy matching. It crashes if something went wrong.
+Still no Req returned.</p></div>
+<div class="paragraph"><p>I feel that this three function interface provides everything
+one would need to comfortably write applications. You can get
+low level and get the query string directly; you can get a list
+of key/value binaries without any additional processing and do it
+on your own; or you can get a processed map that contains Erlang
+terms ready to be used.</p></div>
+<div class="paragraph"><p>I strongly believe that by democratizing the constraints to
+more than just bindings, but also to query string, cookies and
+other key/values in Cowboy, we can allow the developer to quickly
+and easily go from HTTP request to Erlang function calls. The
+constraints are reusable functions that can serve as guards
+against unwanted data, providing convenience in the process.</p></div>
+<div class="paragraph"><p>Your handlers will not look like an endless series of calls
+to get and convert the input data, they will instead be just
+one call at the beginning followed by the actual application
+logic, thanks to constraints and maps.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span>
+ #{<span style="color: #FF6600">name</span><span style="color: #990000">:=</span><span style="color: #009900">Name</span>, <span style="color: #FF6600">email</span><span style="color: #990000">:=</span><span style="color: #009900">Email</span>, <span style="color: #FF6600">choices</span><span style="color: #990000">:=</span><span style="color: #009900">ChoicesList</span>, <span style="color: #FF6600">remember_me</span><span style="color: #990000">:=</span><span style="color: #009900">RememberMe</span>} <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>(<span style="color: #009900">Req</span>, [
+ <span style="font-weight: bold"><span style="color: #000080">name</span></span>, {<span style="color: #FF6600">email</span>, <span style="color: #FF6600">email</span>},
+ {<span style="color: #FF6600">choices</span>, <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> <span style="font-weight: bold"><span style="color: #000000">check_choices</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>, []},
+ {<span style="color: #FF6600">remember_me</span>, <span style="color: #FF6600">boolean</span>, <span style="color: #000080">false</span>}]),
+ <span style="font-weight: bold"><span style="color: #000000">save_choices</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>, <span style="color: #009900">ChoicesList</span>),
+ <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">RememberMe</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">create_account</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>); <span style="color: #000080">true</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">ok</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"blue"</span><span style="color: #990000">&gt;&gt;</span>) <span style="color: #990000">-&gt;</span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">blue</span>};
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"red"</span><span style="color: #990000">&gt;&gt;</span>) <span style="color: #990000">-&gt;</span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">red</span>};
+<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">_</span>) <span style="color: #990000">-&gt;</span> <span style="color: #000080">false</span>;</tt></pre></div></div>
+<div class="paragraph"><p>(Don&#8217;t look too closely at the structure yet.)</p></div>
+<div class="paragraph"><p>As you can see in the above snippet, it becomes really easy
+to go from query string to values. You can also use the map
+directly as it is guaranteed to only contain the keys you
+specified, any extra key is not returned.</p></div>
+<div class="paragraph"><p>This would I believe be a huge step up as we can now
+focus on writing applications instead of translating HTTP
+calls. Cowboy can now take care of it.</p></div>
+<div class="paragraph"><p>And to conclude, this also solves our duplicate keys
+dilemma, as they now automatically become a list of binaries,
+and this list is then checked against constraints that
+will fail if they were not expecting a list. And in the
+example above, it even converts the values to atoms for
+easier manipulation.</p></div>
+<div class="paragraph"><p>As usual, feedback is more than welcome, and I apologize
+for the rocky structure of this post as it contains all the
+thoughts that went into this rather than just the conclusion.</p></div>
+</description> + </item> + + <item> + <title>January 2014 status</title> + <link>http://ninenines.eu/articles/january-2014-status/</link> + <pubDate>Tue, 07 Jan 2014 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/january-2014-status/</guid> + <description><div class="paragraph"><p>I will now be regularly writing posts about project status, plans
+and hopes for the future.</p></div>
+<div class="paragraph"><p>Before that though, there&#8217;s one important news to share.</p></div>
+<div class="paragraph"><p>Until a year ago all development was financed through consulting
+and development services. This worked alright but too much time was
+spent doing things that didn&#8217;t benefit the open source projects.
+And that didn&#8217;t make me happy at all. Because I like being happy
+I stopped that for the most part and spent the year figuring things
+out, experimenting and discussing with people about it.</p></div>
+<div class="paragraph"><p>What makes me happy is answering these "what if" questions.
+Ranch and Cowboy are a direct product of that, as they originate
+from the "what if we could have a server running different protocols
+on different ports but all part of the same application?"; Erlang.mk
+is a bit different: "this works great for me, what if it could
+become the standard solution for building Erlang applications?".</p></div>
+<div class="paragraph"><p>When I successfully answer the question, this becomes a project
+that may end up largely benefiting the Erlang community. I love
+Erlang and I love enabling people to build awesome products based
+on my projects. It&#8217;s a lot more rewarding than activities like
+consulting where you only help one company at a time. And it&#8217;s
+also a much better use of my time as this has a bigger impact on
+the community.</p></div>
+<div class="paragraph"><p>The hard part is to figure out how to be able to spend 100%
+of the time on projects that you basically give away for free,
+and still be able to afford living.</p></div>
+<div class="paragraph"><p>The immediate solution was getting work sponsored by the
+<a href="http://www.leofs.org/">LeoFS project</a>. LeoFS is a great
+distributed file storage that I can only recommend to anyone who
+needs to store files or large pieces of data. The sponsorship
+works pretty great, and spurred development of the SPDY code in
+Cowboy amongst other things, plus a couple upcoming projects
+done more recently and getting a final touch before release.</p></div>
+<div class="paragraph"><p>It turns out sponsoring works great. So I&#8217;m thinking of
+expanding on it and hopefully get enough sponsoring for fulltime
+open source development. So I figured out a few things that
+can give incentive to companies willing to sponsor.</p></div>
+<div class="paragraph"><p>Sponsors can <em>request that a particular version of Cowboy
+be maintained indefinitely</em> (as long as they&#8217;re sponsoring).
+This means fixes will be backported. This doesn&#8217;t include
+features although I can take requests depending on feasability.</p></div>
+<div class="paragraph"><p>Sponsors can <em>have a direct, private line of communication</em>,
+useful when they need help debugging or optimizing their product.</p></div>
+<div class="paragraph"><p>Sponsors can <em>get their name associated with one of the
+project</em> and get a good standing in the community thanks
+to this. They would be featured in the README of the project
+which is viewed by hundreds of developers daily.</p></div>
+<div class="paragraph"><p>Sponsors can <em>be listed on this website</em>. I will modify
+the front page when we get a few more sponsors, they will be
+featured below the carousel of projects.</p></div>
+<div class="paragraph"><p>Please <a href="mailto:[email protected]">contact us</a> if
+you are interested in sponsoring, and say how much you are willing
+to sponsor. The goal here is only to have enough money to make a
+living and attend a few conferences. There&#8217;s an upper limit in the
+amount needed per year, so the more sponsors there are the cheaper
+it becomes to everyone.</p></div>
+<div class="paragraph"><p>The upper limit stems from the new legal entity that will replace
+the current Nine Nines. This is mostly to lower the legal costs and
+simplify the administrative stuff and allow me to dedicate all my
+time on what&#8217;s important. From your point of view it&#8217;s business as
+usual.</p></div>
+<div class="paragraph"><p>Now on to project statuses and future works.</p></div>
+<div class="sect1">
+<h2 id="_cowboy">Cowboy</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Cowboy is getting ready for a 1.0 release. Once multipart support
+is in, all that&#8217;s left is finishing the guide, improving tests and
+finishing moving code to the cowlib project. I hope everything will
+be ready around the time R17B is released.</p></div>
+<div class="paragraph"><p>I already dream of some API breaking changes after 1.0, which
+would essentially become 2.0 when they&#8217;re done. An extensive survey
+will be setup after the 1.0 release to get more information on what
+people like and don&#8217;t like about the API.</p></div>
+<div class="paragraph"><p>And of course, when clients start implementing HTTP/2.0 then we
+will too.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_ranch">Ranch</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Ranch is also getting close to 1.0. I am currently writing a
+test suite for upgrades. After that I also would like to write
+a chaos_monkey test suite and add a getting started chapter to the
+guide.</p></div>
+<div class="paragraph"><p>Ranch is pretty solid otherwise, it&#8217;s hard to foresee new
+features at this point.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_erlang_mk">Erlang.mk</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>I didn&#8217;t expect this project to become popular. Glad it did though.</p></div>
+<div class="paragraph"><p>Windows support is planned, but will require GNU Make 4.
+Thankfully, it&#8217;s available at least through cygwin. Make,
+Git and Erlang will be the only required dependencies
+because the rest of the external calls will be converted to
+using Guile, a Scheme included since GNU Make 4. So it is
+Guile that will download the needed files, magically fill
+the list of modules in the <em>.app</em> file and so on, allowing
+us to provide a truly cross-platform solution without
+losing on the performance we benefit from using Make.</p></div>
+<div class="paragraph"><p>Also note that it is possible to check whether Guile
+is available so we will be able to fallback to the current
+code for older systems.</p></div>
+<div class="paragraph"><p>I am also thinking about adding an extra column to the package
+index, indicating the preferred tag or commit number to be used.
+This would allow us to skip the individual <code>dep</code> lines
+entirely if the information in the package index is good enough.
+And committing that file to your project would be the only thing
+needed to lock the dependencies. Of course if a <code>dep</code>
+line is specified this would instead override the file.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_alien_shaman">Alien Shaman</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>This is the two-parts project requested by the LeoFS team.
+This is essentially a "distributed bigwig". I am hoping to
+have a prototype up in a few days.</p></div>
+<div class="paragraph"><p>Alien is the part that allows writing and enabling probes
+in your nodes. Probes send events which may get filtered before
+being forwarded to their destination. The events may be sent
+to a local process, a remote process, over UDP, TCP or SSL.
+Events may also be received by a process called a relay, which
+may be used to group or aggregate data before it is being sent
+over the network, reducing the footprint overall.</p></div>
+<div class="paragraph"><p>Shaman is the UI for it. It will ultimately be able to display
+any event as long as it&#8217;s configured to do so. Events may be logs,
+numeric values displayed on graphs updated in real time, lists of
+items like processes and so on.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_feedback">Feedback</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>That&#8217;s it for today! There will be another status update once
+Shaman is out. But for now I have to focus on it.</p></div>
+<div class="paragraph"><p>As always, please send feedback on the projects, this post,
+the sponsoring idea, anything really! Thanks.</p></div>
+</div>
+</div>
+</description> + </item> + + <item> + <title>Farwest got funded!</title> + <link>http://ninenines.eu/articles/farwest-funded/</link> + <pubDate>Thu, 27 Jun 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/farwest-funded/</guid> + <description><div class="paragraph"><p>This was a triumph! I&#8217;m making a note here: HUGE SUCCESS!!</p></div>
+<iframe frameborder="0" scrolling="no" height="400px" width"236px" seamless="seamless" src="https://api.bountysource.com/user/fundraisers/83/embed"></iframe>
+<div class="paragraph"><p>It&#8217;s hard to overstate my satisfaction. Thanks to everyone who
+made this possible.</p></div>
+<div class="paragraph"><p>If you have backed this fundraiser, and haven&#8217;t provided your
+personal details yet, please do so quickly so that your rewards
+can be sent!</p></div>
+<div class="paragraph"><p>I am hoping that we will be able to make good use of all that
+money. The details of the expenses will be published regularly
+on the <a href="https://github.com/extend/farwest/wiki/2013-Fundraiser">2013 Fundraiser wiki page</a>,
+giving you full disclosure as to how your money is used.</p></div>
+<div class="paragraph"><p>It will take a little time to get things started, we are in
+summer after all! We will however act quickly to make the
+prototype easy enough to use so that the paid UI work can
+begin. This is also when user contributions will be welcome.</p></div>
+<div class="paragraph"><p>You can see the <a href="https://github.com/extend/farwest/wiki/Roadmap">Roadmap</a>
+to get more information on the current plans. This document will
+get updated as time goes on so check again later to see if you
+can help!</p></div>
+<div class="paragraph"><p>Look at me: still talking when there&#8217;s open source to do!</p></div>
+<div class="paragraph"><p>Thanks again for all your support. I really appreciate it.</p></div>
+</description> + </item> + + <item> + <title>Build Erlang releases with Erlang.mk and Relx</title> + <link>http://ninenines.eu/articles/erlang.mk-and-relx/</link> + <pubDate>Tue, 28 May 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/erlang.mk-and-relx/</guid> + <description><div class="paragraph"><p>Building OTP releases has always been a difficult task. Tools like
+Reltool or Rebar have made this simpler, but
+it&#8217;s no panacea. This article will show you an alternative and
+hopefully much simpler solution.</p></div>
+<div class="paragraph"><p>There is two steps to building a release. First you need to build
+the various OTP applications you want to include in the release. Once
+done, you need to create the release itself, by including the Erlang
+runtime system alongside the applications, a boot script to start the
+node and all its applications, and some configuration files.</p></div>
+<div class="paragraph"><p><a href="https://github.com/extend/erlang.mk">Erlang.mk</a> solves
+the first step. It is an include file for GNU Make. Just
+including it in a Makefile is enough to allow building your project,
+fetching and building dependencies, building documentation, performing
+static analysis and more.</p></div>
+<div class="paragraph"><p><a href="https://github.com/erlware/relx">Relx</a> solves the second
+step. It is a release creation tool, wrapped into a single executable
+file. It doesn&#8217;t require a configuration file. And if you do need one,
+it will be a pretty small one.</p></div>
+<div class="paragraph"><p>Let&#8217;s take a look at the smallest Erlang.mk powered
+Makefile. There is only one thing required: defining the project
+name.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PROJECT =</span> my_project
+
+include erlang.mk</tt></pre></div></div>
+<div class="paragraph"><p>Simply doing this allows you to build your application by typing
+<code>make</code>, running tests using <code>make tests</code>, and
+more. It will even compile your <em>.dtl</em> files found in the
+<em>templates/</em> directory if you are using ErlyDTL!</p></div>
+<div class="paragraph"><p>Let&#8217;s now take a look at a simplified version of the Makefile for
+this website. I only removed a few targets that were off-topic.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PROJECT =</span> ninenines
+
+<span style="color: #009900">DEPS =</span> cowboy erlydtl
+<span style="color: #009900">dep_cowboy =</span> https<span style="color: #990000">:</span>//github.com/extend/cowboy.git 0.8.5
+<span style="color: #009900">dep_erlydtl =</span> https<span style="color: #990000">:</span>//github.com/evanmiller/erlydtl.git 4d0dc8fb
+
+<span style="font-weight: bold"><span style="color: #000080">.PHONY:</span></span> release clean-release
+
+<span style="color: #990000">release:</span> clean-release all projects
+ relx -o rel<span style="color: #990000">/</span><span style="color: #009900">$(PROJECT)</span>
+
+<span style="color: #990000">clean-release:</span> clean-projects
+ rm -rf rel<span style="color: #990000">/</span><span style="color: #009900">$(PROJECT)</span>
+
+include erlang.mk</tt></pre></div></div>
+<div class="paragraph"><p>You can see here how to define dependencies. First you list all
+the dependency names, then you have one line per dependency, giving
+the repository URL and the commit number, tag or branch you want.</p></div>
+<div class="paragraph"><p>Then you can see two targets defined, with <code>release</code>
+becoming the default target, because it was defined first. You can
+override the default target <code>all</code>, which builds the
+application and its dependencies, this way.</p></div>
+<div class="paragraph"><p>And as you can see, the <code>release</code> target uses
+Relx to build a release into the <em>rel/ninenines/</em>
+directory. Let&#8217;s take a look at the configuration file for this release.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">release</span>, {<span style="color: #FF6600">ninenines</span>, <span style="color: #FF0000">"1"</span>}, [<span style="color: #FF6600">ninenines</span>]}<span style="color: #990000">.</span>
+
+{<span style="color: #FF6600">extended_start_script</span>, <span style="color: #000080">true</span>}<span style="color: #990000">.</span>
+{<span style="color: #FF6600">sys_config</span>, <span style="color: #FF0000">"rel/sys.config"</span>}<span style="color: #990000">.</span>
+
+{<span style="color: #FF6600">overlay</span>, [
+ {<span style="color: #FF6600">mkdir</span>, <span style="color: #FF0000">"log"</span>},
+ {<span style="color: #FF6600">copy</span>, <span style="color: #FF0000">"rel/vm.args"</span>,
+ <span style="color: #FF0000">"releases/\{\{release_name\}\}-\{\{release_version\}\}/vm.args"</span>}
+]}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The first line defines a release named <code>ninenines</code>, which
+has a version number <code>"1"</code> and includes one application, also
+named <code>ninenines</code>, although it doesn&#8217;t have to.</p></div>
+<div class="paragraph"><p>We then use the <code>extended_start_script</code> option to tell
+Relx that we would like to have a start script that allows
+us to not only start the release, but do so with the node in the
+background, or also to allow us to connect to a running node, and so on.
+This start script has the same features as the one tools like
+Rebar generates.</p></div>
+<div class="paragraph"><p>The rest of the file just makes sure our configuration files are
+where we expect them. Relx will automatically take care
+of your <em>sys.config</em> file as long as you tell it where to
+find it. The <em>vm.args</em> file used by the extended start script
+needs to be handled more explicitly by using an overlay however.</p></div>
+<div class="paragraph"><p>How does Relx find what applications to include?
+By looking at the application dependencies in the <em>.app</em>
+file of each OTP application. Make sure you put all dependencies in
+there, <em>including</em> library applications, and Relx
+will find everything for you.</p></div>
+<div class="paragraph"><p>For example, this release includes the following applications.
+Only what&#8217;s strictly required.</p></div>
+<div class="listingblock">
+<div class="content">
+<pre><code>compiler-4.9.1 crypto-2.3 kernel-2.16.1 ranch-0.8.3 syntax_tools-1.6.11
+cowboy-0.8.5 erlydtl-0.7.0 ninenines-0.2.0 stdlib-1.19.1</code></pre>
+</div></div>
+<div class="paragraph"><p>The <em>sys.config</em> file is standard and
+<a href="http://www.erlang.org/doc/man/config.html">well documented</a>.
+The <em>vm.args</em> file is just an optionally multiline file
+containing all the flags to pass to the Erlang VM, for example
+<code>-name [email protected] -heart</code>.</p></div>
+<div class="paragraph"><p>Building OTP releases has always been a difficult task. Until now.</p></div>
+</description> + </item> + + <item> + <title>Xerl: intermediate module</title> + <link>http://ninenines.eu/articles/xerl-0.5-intermediate-module/</link> + <pubDate>Mon, 25 Mar 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/xerl-0.5-intermediate-module/</guid> + <description><div class="paragraph"><p>Today we will start the work on the intermediate module
+that will be used to run the code for the expressions found
+in our file&#8217;s body, replacing our interpreter.</p></div>
+<div class="paragraph"><p>This is what we want to have when all the work is done:</p></div>
+<div class="listingblock">
+<div class="content">
+<pre><code>xerl -&gt; tokens -&gt; AST -&gt; intermediate -&gt; cerl</code></pre>
+</div></div>
+<div class="paragraph"><p>Today we will perform this work only on the atomic integer
+expression however, so we will not build any module at the end.
+We have a few more things to take care of before getting there.
+This does mean that we completely break compilation of modules
+though, so hopefully we can resolve that soon.</p></div>
+<div class="paragraph"><p>This intermediate representation is in the form of a module
+which contains a single function: <code>run/0</code>. This function
+contains all the expressions from our Xerl source file.</p></div>
+<div class="paragraph"><p>In the case of a Xerl source file only containing the integer
+<code>42</code>, we will obtain the following module ready to
+be executed:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000080">-module</span></span>(<span style="color: #FF6600">'$xerl_intermediate'</span>)<span style="color: #990000">.</span>
+<span style="font-weight: bold"><span style="color: #000080">-export</span></span>([<span style="font-weight: bold"><span style="color: #000000">run</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">run</span></span>() <span style="color: #990000">-&gt;</span>
+ <span style="color: #993399">42</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Running it will of course give us a result of <code>42</code>,
+the same we had when interpreting expressions.</p></div>
+<div class="paragraph"><p>The resulting Core Erlang code looks like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'$xerl_intermediate'</span> [<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-&gt;</span>
+ <span style="color: #993399">42</span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>The nice thing about doing it like this is that other than the
+definition of the intermediate module and its <code>run/0</code>
+function, we can use the same code we are using for generating
+the final Beam file. It may also be faster than interpreting
+if you have complex modules.</p></div>
+<div class="paragraph"><p>Of course this here only works for the simplest cases, as you
+cannot declare a module or a function inside another Erlang function.
+We will need to wrap these into function calls to the Xerl compiler
+that will take care of compiling them, making them available for
+any subsequent expression. We will also need to pass the environment
+to the <code>run</code> function to keep track of all this.</p></div>
+<div class="paragraph"><p>This does mean that we will have different code for compiling
+<code>fun</code> and <code>mod</code> expressions when creating
+the intermediate module. But the many other expressions don&#8217;t need
+any special care.</p></div>
+<div class="paragraph"><p>Right now we&#8217;ve used the <code>'$xerl_intermediate'</code> atom
+for the intermediate module name because we only have one, but we
+will need to have a more random name later on when we&#8217;ll implement
+modules this way.</p></div>
+<div class="paragraph"><p>The attentive mind will know by now that when compiling a Xerl
+file containing one module, we will need to compile two intermediate
+modules: one for the file body, and one for the module&#8217;s body. Worry
+not though, if we only detect <code>mod</code> instructions in the file
+body, we can just skip this phase.</p></div>
+<div class="paragraph"><p>While we&#8217;re at it, we&#8217;ll modify our code generator to handle lists
+of expressions, which didn&#8217;t actually work with integer literals
+before.</p></div>
+<div class="paragraph"><p>We&#8217;re going to use Core Erlang sequences for running the many
+expressions. Sequences work like <code>let</code>, except no value
+is actually bound. Perfect for our case, since we don&#8217;t support
+binding values at this time anyway.</p></div>
+<div class="paragraph"><p>Sequences have an argument and a body, both being Core Erlang
+expressions. The simplest way to have many expressions is to use
+a simple expression for the argument and a sequence for the rest
+of the expressions. When we encounter the last expression in the
+list, we do not create a sequence.</p></div>
+<div class="paragraph"><p>The result is this very simple function:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>([<span style="color: #009900">Expr</span>]) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">expr</span></span>(<span style="color: #009900">Expr</span>);
+<span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>([<span style="color: #009900">Expr</span>|<span style="color: #009900">Exprs</span>]) <span style="color: #990000">-&gt;</span>
+ <span style="color: #009900">Arg</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">expr</span></span>(<span style="color: #009900">Expr</span>),
+ <span style="color: #009900">Body</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>(<span style="color: #009900">Exprs</span>),
+ <span style="font-weight: bold"><span style="color: #000000">cerl:c_seq</span></span>(<span style="color: #009900">Arg</span>, <span style="color: #009900">Body</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>In the case of our example above, a sequence will not be created,
+we only have one expression. If we were to have <code>42, 43, 44</code>
+in our Xerl source file, we would have a result equivalent to the
+following before optimization:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000080">-module</span></span>(<span style="color: #FF6600">'$xerl_intermediate'</span>)<span style="color: #990000">.</span>
+<span style="font-weight: bold"><span style="color: #000080">-export</span></span>([<span style="font-weight: bold"><span style="color: #000000">run</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">run</span></span>() <span style="color: #990000">-&gt;</span>
+ <span style="color: #993399">42</span>,
+ <span style="color: #993399">43</span>,
+ <span style="color: #993399">44</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And the result is of course <code>44</code>.</p></div>
+<div class="paragraph"><p>The resulting Core Erlang code looks like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'$xerl_intermediate'</span> [<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-&gt;</span>
+ <span style="color: #FF6600">do</span> <span style="color: #993399">42</span>
+ <span style="color: #FF6600">do</span> <span style="color: #993399">43</span>
+ <span style="color: #993399">44</span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Feels very lisp-y, right? Yep.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.5/">View the source</a>
+</p>
+</li>
+</ul></div>
+</description> + </item> + + <item> + <title>Xerl: expression separator</title> + <link>http://ninenines.eu/articles/xerl-0.4-expression-separator/</link> + <pubDate>Fri, 01 Mar 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/xerl-0.4-expression-separator/</guid> + <description><div class="paragraph"><p>As promised we are adding an expression separator this time.
+This will be short and easy.</p></div>
+<div class="paragraph"><p>In the tokenizer we only need to add a line recognizing the
+comma as a valid token.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>, <span style="color: #990000">:</span> {<span style="color: #FF6600">token</span>, {<span style="color: #FF6600">','</span>, <span style="color: #009900">TokenLine</span>}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Then we need to change the following lines in the parser:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$2'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And add a comma between the expressions on the second line:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$3'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>That takes care of everything except the optional trailing
+comma at the end of our lists of expressions. We just need an
+additional rule to take care of this.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>That&#8217;s it.</p></div>
+<div class="paragraph"><p>Wondering why we don&#8217;t have this optional trailing comma in
+Erlang considering how easy it was and the number of people
+complaining about it? Yeah, me too. But that&#8217;s for someone else
+to answer.</p></div>
+<div class="paragraph"><p>Another change I want to talk about is a simple modification
+of the compiler code to use an <code>#env{}</code> record for
+tracking state instead of passing around individual variables.
+This will be required later on when we make modules into proper
+expressions so I thought it was a good idea to anticipate.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.4/">View the source</a>
+</p>
+</li>
+</ul></div>
+</description> + </item> + + <item> + <title>Erlang Scalability</title> + <link>http://ninenines.eu/articles/erlang-scalability/</link> + <pubDate>Mon, 18 Feb 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/erlang-scalability/</guid> + <description><div class="paragraph"><p>I would like to share some experience and theories on
+Erlang scalability.</p></div>
+<div class="paragraph"><p>This will be in the form of a series of hints, which
+may or may not be accompanied with explanations as to why
+things are this way, or how they improve or reduce the scalability
+of a system. I will try to do my best to avoid giving falsehoods,
+even if that means a few things won&#8217;t be explained.</p></div>
+<div class="sect1">
+<h2 id="_nifs">NIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>NIFs are considered harmful. I don&#8217;t know any single NIF-based
+library that I would recommend. That doesn&#8217;t mean they should
+all be avoided, just that if you&#8217;re going to want your system to
+scale, you probably shouldn&#8217;t use a NIF.</p></div>
+<div class="paragraph"><p>A common case for using NIFs is JSON processing. The problem
+is that JSON is a highly inefficient data structure (similar
+in inefficiency to XML, although perhaps not as bad). If you can
+avoid using JSON, you probably should. MessagePack can replace
+it in many situations.</p></div>
+<div class="paragraph"><p>Long-running NIFs will take over a scheduler and prevent Erlang
+from efficiently handling many processes.</p></div>
+<div class="paragraph"><p>Short-running NIFs will still confuse the scheduler if they
+take more than a few microseconds to run.</p></div>
+<div class="paragraph"><p>Threaded NIFs, or the use of the <code>enif_consume_timeslice</code>
+might help allievate this problem, but they&#8217;re not a silver bullet.</p></div>
+<div class="paragraph"><p>And as you already know, a crashing NIF will take down your VM,
+destroying any claims you may have at being scalable.</p></div>
+<div class="paragraph"><p>Never use a NIF because "C is fast". This is only true in
+single-threaded programs.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_bifs">BIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>BIFs can also be harmful. While they are generally better than
+NIFs, they are not perfect and some of them might have harmful
+effects on the scheduler.</p></div>
+<div class="paragraph"><p>A great example of this is the <code>erlang:decode_packet/3</code>
+BIF, when used for HTTP request or response decoding. Avoiding
+its use in <em>Cowboy</em> allowed us to see a big increase in
+the number of requests production systems were able to handle,
+up to two times the original amount. Incidentally this is something
+that is impossible to detect using synthetic benchmarks.</p></div>
+<div class="paragraph"><p>BIFs that return immediately are perfectly fine though.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_binary_strings">Binary strings</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Binary strings use less memory, which means you spend less time
+allocating memory compared to list-based strings. They are also
+more natural for strings manipulation because they are optimized
+for appending (as opposed to prepending for lists).</p></div>
+<div class="paragraph"><p>If you can process a binary string using a single match context,
+then the code will run incredibly fast. The effects will be much
+increased if the code was compiled using HiPE, even if your Erlang
+system isn&#8217;t compiled natively.</p></div>
+<div class="paragraph"><p>Avoid using <code>binary:split</code> or <code>binary:replace</code>
+if you can avoid it. They have a certain overhead due to supporting
+many options that you probably don&#8217;t need for most operations.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_buffering_and_streaming">Buffering and streaming</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Use binaries. They are great for appending, and it&#8217;s a direct copy
+from what you receive from a stream (usually a socket or a file).</p></div>
+<div class="paragraph"><p>Be careful to not indefinitely receive data, as you might end up
+having a single binary taking up huge amounts of memory.</p></div>
+<div class="paragraph"><p>If you stream from a socket and know how much data you expect,
+then fetch that data in a single <code>recv</code> call.</p></div>
+<div class="paragraph"><p>Similarly, if you can use a single <code>send</code> call, then
+you should do so, to avoid going back and forth unnecessarily between
+your Erlang process and the Erlang port for your socket.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_list_and_binary_comprehensions">List and binary comprehensions</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Prefer list comprehensions over <code>lists:map/2</code>. The
+compiler will be able to optimize your code greatly, for example
+not creating the result if you don&#8217;t need it. As time goes on,
+more optimizations will be added to the compiler and you will
+automatically benefit from them.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_gen_server_is_no_silver_bullet">gen_server is no silver bullet</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>It&#8217;s a bad idea to use <code>gen_server</code> for everything.
+For two reasons.</p></div>
+<div class="paragraph"><p>There is an overhead everytime the <code>gen_server</code> receives
+a call, a cast or a simple message. It can be a problem if your
+<code>gen_server</code> is in a critical code path where speed
+is all that matters. Do not hesitate to create other kinds of
+processes where it makes sense. And depending on the kind of process,
+you might want to consider making them special processes, which
+would essentially behave the same as a <code>gen_server</code>.</p></div>
+<div class="paragraph"><p>A common mistake is to have a unique <code>gen_server</code> to
+handle queries from many processes. This generally becomes the
+biggest bottleneck you&#8217;ll want to fix. You should try to avoid
+relying on a single process, using a pool if you can.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_supervisor_and_monitoring">Supervisor and monitoring</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>A <code>supervisor</code> is also a <code>gen_server</code>,
+so the previous points also apply to them.</p></div>
+<div class="paragraph"><p>Sometimes you&#8217;re in a situation where you have supervised
+processes but also want to monitor them in one or more other
+processes, effectively duplicating the work. The supervisor
+already knows when processes die, why not use this to our
+advantage?</p></div>
+<div class="paragraph"><p>You can create a custom supervisor process that will perform
+both the supervision and handle exit and other events, allowing
+to avoid the combination of supervising and monitoring which
+can prove harmful when many processes die at once, or when you
+have many short lived processes.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_ets_for_lolspeed_tm">ets for LOLSPEED(tm)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>If you have data queried or modified by many processes, then
+<code>ets</code> public or protected tables will give you the
+performance boost you require. Do not forget to set the
+<code>read_concurrency</code> or <code>write_concurrency</code>
+options though.</p></div>
+<div class="paragraph"><p>You might also be thrilled to know that Erlang R16B will feature
+a big performance improvement for accessing <code>ets</code> tables
+concurrently.</p></div>
+</div>
+</div>
+</description> + </item> + + <item> + <title>Xerl: atomic expressions</title> + <link>http://ninenines.eu/articles/xerl-0.3-atomic-expressions/</link> + <pubDate>Mon, 18 Feb 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/xerl-0.3-atomic-expressions/</guid> + <description><div class="paragraph"><p>We will be adding atomic integer expressions to our language.
+These look as follow in Erlang:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">42</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And the result of this expression is of course 42.</p></div>
+<div class="paragraph"><p>We will be running this expression at compile time, since we
+don&#8217;t have the means to run code at runtime yet. This will of
+course result in no module being compiled, but that&#8217;s OK, it will
+allow us to discuss a few important things we&#8217;ll have to plan for
+later on.</p></div>
+<div class="paragraph"><p>First, we must of course accept integers in the tokenizer.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #009900">D</span>}<span style="color: #990000">+</span> <span style="color: #990000">:</span> {<span style="color: #FF6600">token</span>, {<span style="font-weight: bold"><span style="color: #000080">integer</span></span>, <span style="color: #009900">TokenLine</span>, <span style="font-weight: bold"><span style="color: #000080">list_to_integer</span></span>(<span style="color: #009900">TokenChars</span>)}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>We must then accept atomic integer expressions in the parser.
+This is a simple change. The integer token is terminal so we need
+to add it to the list of terminals, and then we only need to add
+it as a possible expression.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">expr</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">integer</span> <span style="color: #990000">:</span> <span style="color: #FF6600">'$1'</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>A file containing only the number 42 (with no terminating dot)
+will give the following result when parsing it. This is incidentally
+the same result as when tokenizing.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>We must then evaluate it. We&#8217;re going to interpret it for now.
+Since the result of this expression is not stored in a variable,
+we are going to simply print it on the screen and discard it.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, [{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>, <span style="color: #990000">_</span>, <span style="color: #009900">Int</span>}|<span style="color: #009900">Tail</span>], <span style="color: #009900">Modules</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"integer ~p~n"</span>, [<span style="color: #009900">Int</span>]),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Tail</span>, <span style="color: #009900">Modules</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You might think by now that what we&#8217;ve done so far this time
+is useless. It brings up many interesting questions though.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+What happens if a file contains two integers?
+</p>
+</li>
+<li>
+<p>
+Can we live without expression separators?
+</p>
+</li>
+<li>
+<p>
+Do we need an interpreter for the compile step?
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>This is what happens when we create a file that contains two
+integers on two separate lines:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>},{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">2</span>,<span style="color: #993399">43</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>And on the same lines:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>},{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">43</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>Does this mean we do not need separators between expressions?
+Not quite. The <code>+</code> and <code>-</code> operators are an
+example of why we can&#8217;t have nice things. They are ambiguous. They
+have two different meanings: make an atomic integer positive or
+negative, or perform an addition or a substraction between two
+integers. Without a separator you won&#8217;t be able to know if the
+following snippet is one or two expressions:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">42</span> <span style="color: #990000">-</span> <span style="color: #993399">12</span></tt></pre></div></div>
+<div class="paragraph"><p>Can we use the line ending as an expression separator then?
+Some languages make whitespace important, often the line
+separator becomes the expression separator. I do not think this
+is the best idea, it can lead to errors. For example the following
+snippet would be two expressions:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Var</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">some_module:some_function</span></span>() <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000000">some_module:other_function</span></span>()
+ <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000000">another_module:another_function</span></span>()</tt></pre></div></div>
+<div class="paragraph"><p>It is not obvious what would happen unless you are a veteran
+of the language, and so we will not go down that road. We will use
+an expression separator just like in Erlang: the comma. We will
+however allow a trailing comma to make copy pasting code easier,
+even if this means some old academics guy will go nuts about it
+later on. This trailing comma will be optional and simply discarded
+by the parser when encountered. We will implement this next.</p></div>
+<div class="paragraph"><p>The question as to how we will handle running expressions
+remains. We have two choices here: we can write an interpreter,
+or we can compile the code and run it. Writing an interpreter
+would require us to do twice the work, and we are lazy, so we will
+not do that.</p></div>
+<div class="paragraph"><p>You might already know that Erlang does not use the same code
+for compiling and for evaluating commands in the shell. The main
+reason for this is that in Erlang everything isn&#8217;t an expression.
+Indeed, the compiler compiles forms which contain expressions,
+but you can&#8217;t have forms in the shell.</p></div>
+<div class="paragraph"><p>How are we going to compile the code that isn&#8217;t part of a module
+then? What do we need to run at compile-time, anyway? The body of
+the file itself, of course. The body of module declarations. That&#8217;s
+about it.</p></div>
+<div class="paragraph"><p>For the file itself, we can simply compile it as a big function
+that will be executed. Then, everytime we encounter a module
+declaration, we will run the compiler on its body, making its body
+essentially a big function that will be executed. The same mechanism
+will be applied when we encounter a module declaration at runtime.</p></div>
+<div class="paragraph"><p>At runtime there&#8217;s nothing else for us to do, the result of this
+operation will load all the compiled modules. At compile time we
+will also want to save them to a file. We&#8217;ll see later how we can
+do that.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.3/">View the source</a>
+</p>
+</li>
+</ul></div>
+</description> + </item> + + <item> + <title>Xerl: two modules</title> + <link>http://ninenines.eu/articles/xerl-0.2-two-modules/</link> + <pubDate>Sun, 03 Feb 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/xerl-0.2-two-modules/</guid> + <description><div class="paragraph"><p>Everything is an expression.</p></div>
+<div class="paragraph"><p>This sentence carries profound meaning. We will invoke it many
+times over the course of these articles.</p></div>
+<div class="paragraph"><p>If everything is an expression, then the language shouldn&#8217;t have
+any problem with me defining two modules in the same source file.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">first_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+
+<span style="color: #FF6600">mod</span> <span style="color: #FF6600">second_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Likewise, it shouldn&#8217;t have any problem with me defining a
+module inside another module.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">out_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+ <span style="color: #FF6600">mod</span> <span style="color: #FF6600">in_module</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Of course, in the context of the Erlang VM, these two snippets
+are equivalent; there is nothing preventing you from calling the
+<code>in_module</code> module from any other module. The <code>mod</code>
+instruction means a module should be created in the Erlang VM,
+with no concept of scope attached.</p></div>
+<div class="paragraph"><p>Still we need to handle both. To do this we will add a step
+between the parser and the code generator that will walk over the
+abstract syntax tree, from here onward shortened as <em>AST</em>,
+and transform the AST by executing it where applicable.</p></div>
+<div class="paragraph"><p>What happens when you execute a <code>mod</code> instruction?
+A module is created. Since we are compiling, that simply means
+the compiler will branch out and create a module.</p></div>
+<div class="paragraph"><p>If everything is an expression, does that mean this will allow
+me to create modules at runtime using the same syntax? Yes, but
+let&#8217;s not get ahead of ourselves yet.</p></div>
+<div class="paragraph"><p>For now we will just iterate over the AST, and will compile
+a module for each <code>mod</code> found. Modules cannot contain
+expressions yet, so there&#8217;s no need to recurse over it at this
+point. This should solve the compilation of our first snippet.</p></div>
+<div class="paragraph"><p>The <code>compile/1</code> function becomes:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">compile</span></span>(<span style="color: #009900">Filename</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Compiling ~s...~n"</span>, [<span style="color: #009900">Filename</span>]),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Src</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">file:read_file</span></span>(<span style="color: #009900">Filename</span>),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Tokens</span>, <span style="color: #990000">_</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_lexer:string</span></span>(<span style="font-weight: bold"><span style="color: #000080">binary_to_list</span></span>(<span style="color: #009900">Src</span>)),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Exprs</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_parser:parse</span></span>(<span style="color: #009900">Tokens</span>),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Exprs</span>, [])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #990000">_</span>, [], <span style="color: #009900">Modules</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Done...~n"</span>),
+ {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">lists:reverse</span></span>(<span style="color: #009900">Modules</span>)};
+<span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, [<span style="color: #009900">Expr</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">mod</span>, <span style="color: #990000">_</span>, {<span style="font-weight: bold"><span style="color: #000080">atom</span></span>, <span style="color: #990000">_</span>, <span style="color: #009900">Name</span>}, []}|<span style="color: #009900">Tail</span>], <span style="color: #009900">Modules</span>) <span style="color: #990000">-&gt;</span>
+ {<span style="color: #FF6600">ok</span>, [<span style="color: #009900">Core</span>]} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_codegen:exprs</span></span>([<span style="color: #009900">Expr</span>]),
+ {<span style="color: #FF6600">ok</span>, [{<span style="color: #009900">Name</span>, []}]} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">core_lint:module</span></span>(<span style="color: #009900">Core</span>),
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"~s~n"</span>, [<span style="font-weight: bold"><span style="color: #000000">core_pp:format</span></span>(<span style="color: #009900">Core</span>)]),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #990000">_</span>, <span style="color: #009900">Beam</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">compile:forms</span></span>(<span style="color: #009900">Core</span>,
+ [<span style="font-weight: bold"><span style="color: #000080">binary</span></span>, <span style="color: #FF6600">from_core</span>, <span style="color: #FF6600">return_errors</span>, {<span style="color: #FF6600">source</span>, <span style="color: #009900">Filename</span>}]),
+ {<span style="color: #FF6600">module</span>, <span style="color: #009900">Name</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">code:load_binary</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Filename</span>, <span style="color: #009900">Beam</span>),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Tail</span>, [<span style="color: #009900">Name</span>|<span style="color: #009900">Modules</span>])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Running this compiler over the first snippet yields the following
+result:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Compiling</span> <span style="font-weight: bold"><span style="color: #000000">test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span><span style="color: #990000">...</span>
+<span style="color: #FF6600">module</span> <span style="color: #FF6600">'first_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'first_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'first_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="color: #FF6600">module</span> <span style="color: #FF6600">'second_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'second_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'second_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="color: #009900">Done</span><span style="color: #990000">...</span>
+{<span style="color: #FF6600">ok</span>,[<span style="color: #FF6600">first_module</span>,<span style="color: #FF6600">second_module</span>]}</tt></pre></div></div>
+<div class="paragraph"><p>Everything looks fine. And we can check that the two modules have
+been loaded into the VM:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">9</span><span style="color: #990000">&gt;</span> <span style="color: #FF6600">m</span>(<span style="color: #FF6600">first_module</span>)<span style="color: #990000">.</span>
+<span style="color: #009900">Module</span> <span style="color: #FF6600">first_module</span> <span style="color: #FF6600">compiled</span><span style="color: #990000">:</span> <span style="color: #009900">Date</span><span style="color: #990000">:</span> <span style="color: #009900">February</span> <span style="color: #993399">2</span> <span style="color: #993399">2013</span>, <span style="color: #009900">Time</span><span style="color: #990000">:</span> <span style="color: #993399">14.56</span>
+<span style="color: #009900">Compiler</span> <span style="color: #FF6600">options</span><span style="color: #990000">:</span> [<span style="color: #FF6600">from_core</span>]
+<span style="color: #009900">Object</span> <span style="font-weight: bold"><span style="color: #000000">file: test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span>
+<span style="color: #009900">Exports</span><span style="color: #990000">:</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>
+<span style="color: #FF6600">ok</span>
+<span style="color: #993399">10</span><span style="color: #990000">&gt;</span> <span style="color: #FF6600">m</span>(<span style="color: #FF6600">second_module</span>)<span style="color: #990000">.</span>
+<span style="color: #009900">Module</span> <span style="color: #FF6600">second_module</span> <span style="color: #FF6600">compiled</span><span style="color: #990000">:</span> <span style="color: #009900">Date</span><span style="color: #990000">:</span> <span style="color: #009900">February</span> <span style="color: #993399">2</span> <span style="color: #993399">2013</span>, <span style="color: #009900">Time</span><span style="color: #990000">:</span> <span style="color: #993399">14.56</span>
+<span style="color: #009900">Compiler</span> <span style="color: #FF6600">options</span><span style="color: #990000">:</span> [<span style="color: #FF6600">from_core</span>]
+<span style="color: #009900">Object</span> <span style="font-weight: bold"><span style="color: #000000">file: test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span>
+<span style="color: #009900">Exports</span><span style="color: #990000">:</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>
+<span style="color: #FF6600">ok</span></tt></pre></div></div>
+<div class="paragraph"><p>So far so good!</p></div>
+<div class="paragraph"><p>What about the second snippet? It brings up many questions. What
+happens once a <code>mod</code> expression has been executed at
+compile time? If it&#8217;s an expression then it has to have a result,
+right? Right. We are still a bit lacking with expressions for now,
+though, so let&#8217;s get back to it after we add more.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.2/">View the source</a>
+</p>
+</li>
+</ul></div>
+</description> + </item> + + <item> + <title>Xerl: empty modules</title> + <link>http://ninenines.eu/articles/xerl-0.1-empty-modules/</link> + <pubDate>Wed, 30 Jan 2013 00:00:00 +0100</pubDate> + + <guid>http://ninenines.eu/articles/xerl-0.1-empty-modules/</guid> + <description><div class="paragraph"><p>Let&#8217;s build a programming language. I call it Xerl: eXtended ERLang.
+It&#8217;ll be an occasion for us to learn a few things, especially me.</p></div>
+<div class="paragraph"><p>Unlike in Erlang, in this language, everything is an expression.
+This means that modules and functions are expression, and indeed that
+you can have more than one module per file.</p></div>
+<div class="paragraph"><p>We are just starting, so let&#8217;s no go ahead of ourselves here. We&#8217;ll
+begin with writing the code allowing us to compile an empty module.</p></div>
+<div class="paragraph"><p>We will compile to Core Erlang: this is one of the many intermediate
+step your Erlang code compiles to before it becomes BEAM machine code.
+Core Erlang is a very neat language for machine generated code, and we
+will learn many things about it.</p></div>
+<div class="paragraph"><p>Today we will only focus on compiling the following code:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">my_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Compilation will be done in a few steps. First, the source file will
+be transformed in a tree of tokens by the lexer. Then, the parser will
+use that tree of tokens and convert it to the AST, bringing semantical
+meaning to our representation. Finally, the code generator will transform
+this AST to Core Erlang AST, which will then be compiled.</p></div>
+<div class="paragraph"><p>We will use <em>leex</em> for the lexer. This lexer uses .xrl files
+which are then compiled to .erl files that you can then compile to BEAM.
+The file is divided in three parts: definitions, rules and Erlang code.
+Definitions and Erlang code are obvious; rules are what concerns us.</p></div>
+<div class="paragraph"><p>We only need two things: atoms and whitespaces. Atoms are a lowercase
+letter followed by any letter, number, _ or @. Whitespace is either a
+space, an horizontal tab, \r or \n. There exists other kinds of whitespaces
+but we simply do not allow them in the Xerl language.</p></div>
+<div class="paragraph"><p>Rules consist of a regular expression followed by Erlang code. The
+latter must return a token representation or the atom <code>skip_token</code>.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #009900">L</span>}{<span style="color: #009900">A</span>}<span style="color: #990000">*</span> <span style="color: #990000">:</span>
+ <span style="color: #009900">Atom</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000080">list_to_atom</span></span>(<span style="color: #009900">TokenChars</span>),
+ {<span style="color: #FF6600">token</span>, <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">reserved_word</span></span>(<span style="color: #009900">Atom</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ <span style="color: #000080">true</span> <span style="color: #990000">-&gt;</span> {<span style="color: #009900">Atom</span>, <span style="color: #009900">TokenLine</span>};
+ <span style="color: #000080">false</span> <span style="color: #990000">-&gt;</span> {<span style="font-weight: bold"><span style="color: #000080">atom</span></span>, <span style="color: #009900">TokenLine</span>, <span style="color: #009900">Atom</span>}
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>}<span style="color: #990000">.</span>
+
+{<span style="color: #009900">WS</span>}<span style="color: #990000">+</span> <span style="color: #990000">:</span> <span style="color: #FF6600">skip_token</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The first rule matches an atom, which is converted to either a special
+representation for reserved words, or an atom tuple. The
+<code>TokenChars</code> variable represents the match as a string, and
+the <code>TokenLine</code> variable contains the line number.
+<a href="https://github.com/extend/xerl/blob/0.1/src/xerl_lexer.xrl">View the complete file</a>.</p></div>
+<div class="paragraph"><p>We obtain the following result from the lexer:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="color: #FF6600">mod</span>,<span style="color: #993399">1</span>},{<span style="font-weight: bold"><span style="color: #000080">atom</span></span>,<span style="color: #993399">1</span>,<span style="color: #FF6600">my_module</span>},{<span style="color: #FF6600">'begin'</span>,<span style="color: #993399">2</span>},{<span style="color: #FF6600">'end'</span>,<span style="color: #993399">3</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>The second step is to parse this list of tokens to add semantic meaning
+and generate what is called an <em>abstract syntax tree</em>. We will be
+using the <em>yecc</em> parser generator for this. This time it will take
+.yrl files but the process is the same as before. The file is a little
+more complex than for the lexer, we need to define at the very least
+terminals, nonterminals and root symbols, the grammar itself, and
+optionally some Erlang code.</p></div>
+<div class="paragraph"><p>To compile our module, we need a few things. First, everything is an
+expression. We thus need list of expressions and individual expressions.
+We will support a single expression for now, the <code>mod</code>
+expression which defines a module. And that&#8217;s it! We end up with the
+following grammar:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$2'</span>]<span style="color: #990000">.</span>
+
+<span style="color: #FF6600">expr</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">module</span> <span style="color: #990000">:</span> <span style="color: #FF6600">'$1'</span><span style="color: #990000">.</span>
+
+<span style="color: #FF6600">module</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">'mod'</span> <span style="font-weight: bold"><span style="color: #000080">atom</span></span> <span style="color: #FF6600">'begin'</span> <span style="color: #FF6600">'end'</span> <span style="color: #990000">:</span>
+ {<span style="color: #FF6600">'mod'</span>, <span style="font-weight: bold"><span style="color: #000080">?line</span></span>(<span style="color: #FF6600">'$1'</span>), <span style="color: #FF6600">'$2'</span>, []}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p><a href="https://github.com/extend/xerl/blob/0.1/src/xerl_parser.yrl">View the complete file</a>.</p></div>
+<div class="paragraph"><p>We obtain the following result from the parser:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="color: #FF6600">mod</span>,<span style="color: #993399">1</span>,{<span style="font-weight: bold"><span style="color: #000080">atom</span></span>,<span style="color: #993399">1</span>,<span style="color: #FF6600">my_module</span>},[]}]</tt></pre></div></div>
+<div class="paragraph"><p>We obtain a list of a single <code>mod</code> expression. Just like
+we wanted. Last step is generating the Core Erlang code from it.</p></div>
+<div class="paragraph"><p>Code generation generally is comprised of several steps. We will
+discuss these in more details later on. For now, we will focus on the
+minimal needed for successful compilation.</p></div>
+<div class="paragraph"><p>We can use the <code>cerl</code> module to generate Core Erlang AST.
+We will simply be using functions, which allows us to avoid learning
+and keeping up to date with the internal representation.</p></div>
+<div class="paragraph"><p>There&#8217;s one important thing to do when generating Core Erlang AST
+for a module: create the <code>module_info/{0,1}</code> functions.
+Indeed, these are added to Erlang before it becomes Core Erlang, and
+so we need to replicate this ourselves. Do not be concerned however,
+as this only takes a few lines of extra code.</p></div>
+<div class="paragraph"><p>As you can see by
+<a href="https://github.com/extend/xerl/blob/0.1/src/xerl_codegen.erl">looking at the complete file</a>,
+the code generator echoes the grammar we defined in the parser, and
+simply applies the appropriate Core Erlang functions for each expressions.</p></div>
+<div class="paragraph"><p>We obtain the following pretty-printed Core Erlang generated code:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'my_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'empty_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-&gt;</span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'empty_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>For convenience I added all the steps in a <code>xerl:compile/1</code>
+function that you can use against your own .xerl files.</p></div>
+<div class="paragraph"><p>That&#8217;s it for today! We will go into more details over each steps in
+the next few articles.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.1/">View the source</a>
+</p>
+</li>
+</ul></div>
+</description> + </item> + + </channel> +</rss>
\ No newline at end of file diff --git a/articles/january-2014-status/index.html b/articles/january-2014-status/index.html new file mode 100644 index 00000000..8c10f522 --- /dev/null +++ b/articles/january-2014-status/index.html @@ -0,0 +1,299 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: January 2014 status</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>January 2014 status</span></h1> + <p class="date"> + <span class="day">07</span> + <span class="month">Jan</span> + </p> +</header> + +<div class="paragraph"><p>I will now be regularly writing posts about project status, plans
+and hopes for the future.</p></div>
+<div class="paragraph"><p>Before that though, there’s one important news to share.</p></div>
+<div class="paragraph"><p>Until a year ago all development was financed through consulting
+and development services. This worked alright but too much time was
+spent doing things that didn’t benefit the open source projects.
+And that didn’t make me happy at all. Because I like being happy
+I stopped that for the most part and spent the year figuring things
+out, experimenting and discussing with people about it.</p></div>
+<div class="paragraph"><p>What makes me happy is answering these "what if" questions.
+Ranch and Cowboy are a direct product of that, as they originate
+from the "what if we could have a server running different protocols
+on different ports but all part of the same application?"; Erlang.mk
+is a bit different: "this works great for me, what if it could
+become the standard solution for building Erlang applications?".</p></div>
+<div class="paragraph"><p>When I successfully answer the question, this becomes a project
+that may end up largely benefiting the Erlang community. I love
+Erlang and I love enabling people to build awesome products based
+on my projects. It’s a lot more rewarding than activities like
+consulting where you only help one company at a time. And it’s
+also a much better use of my time as this has a bigger impact on
+the community.</p></div>
+<div class="paragraph"><p>The hard part is to figure out how to be able to spend 100%
+of the time on projects that you basically give away for free,
+and still be able to afford living.</p></div>
+<div class="paragraph"><p>The immediate solution was getting work sponsored by the
+<a href="http://www.leofs.org/">LeoFS project</a>. LeoFS is a great
+distributed file storage that I can only recommend to anyone who
+needs to store files or large pieces of data. The sponsorship
+works pretty great, and spurred development of the SPDY code in
+Cowboy amongst other things, plus a couple upcoming projects
+done more recently and getting a final touch before release.</p></div>
+<div class="paragraph"><p>It turns out sponsoring works great. So I’m thinking of
+expanding on it and hopefully get enough sponsoring for fulltime
+open source development. So I figured out a few things that
+can give incentive to companies willing to sponsor.</p></div>
+<div class="paragraph"><p>Sponsors can <em>request that a particular version of Cowboy
+be maintained indefinitely</em> (as long as they’re sponsoring).
+This means fixes will be backported. This doesn’t include
+features although I can take requests depending on feasability.</p></div>
+<div class="paragraph"><p>Sponsors can <em>have a direct, private line of communication</em>,
+useful when they need help debugging or optimizing their product.</p></div>
+<div class="paragraph"><p>Sponsors can <em>get their name associated with one of the
+project</em> and get a good standing in the community thanks
+to this. They would be featured in the README of the project
+which is viewed by hundreds of developers daily.</p></div>
+<div class="paragraph"><p>Sponsors can <em>be listed on this website</em>. I will modify
+the front page when we get a few more sponsors, they will be
+featured below the carousel of projects.</p></div>
+<div class="paragraph"><p>Please <a href="mailto:[email protected]">contact us</a> if
+you are interested in sponsoring, and say how much you are willing
+to sponsor. The goal here is only to have enough money to make a
+living and attend a few conferences. There’s an upper limit in the
+amount needed per year, so the more sponsors there are the cheaper
+it becomes to everyone.</p></div>
+<div class="paragraph"><p>The upper limit stems from the new legal entity that will replace
+the current Nine Nines. This is mostly to lower the legal costs and
+simplify the administrative stuff and allow me to dedicate all my
+time on what’s important. From your point of view it’s business as
+usual.</p></div>
+<div class="paragraph"><p>Now on to project statuses and future works.</p></div>
+<div class="sect1">
+<h2 id="_cowboy">Cowboy</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Cowboy is getting ready for a 1.0 release. Once multipart support
+is in, all that’s left is finishing the guide, improving tests and
+finishing moving code to the cowlib project. I hope everything will
+be ready around the time R17B is released.</p></div>
+<div class="paragraph"><p>I already dream of some API breaking changes after 1.0, which
+would essentially become 2.0 when they’re done. An extensive survey
+will be setup after the 1.0 release to get more information on what
+people like and don’t like about the API.</p></div>
+<div class="paragraph"><p>And of course, when clients start implementing HTTP/2.0 then we
+will too.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_ranch">Ranch</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Ranch is also getting close to 1.0. I am currently writing a
+test suite for upgrades. After that I also would like to write
+a chaos_monkey test suite and add a getting started chapter to the
+guide.</p></div>
+<div class="paragraph"><p>Ranch is pretty solid otherwise, it’s hard to foresee new
+features at this point.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_erlang_mk">Erlang.mk</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>I didn’t expect this project to become popular. Glad it did though.</p></div>
+<div class="paragraph"><p>Windows support is planned, but will require GNU Make 4.
+Thankfully, it’s available at least through cygwin. Make,
+Git and Erlang will be the only required dependencies
+because the rest of the external calls will be converted to
+using Guile, a Scheme included since GNU Make 4. So it is
+Guile that will download the needed files, magically fill
+the list of modules in the <em>.app</em> file and so on, allowing
+us to provide a truly cross-platform solution without
+losing on the performance we benefit from using Make.</p></div>
+<div class="paragraph"><p>Also note that it is possible to check whether Guile
+is available so we will be able to fallback to the current
+code for older systems.</p></div>
+<div class="paragraph"><p>I am also thinking about adding an extra column to the package
+index, indicating the preferred tag or commit number to be used.
+This would allow us to skip the individual <code>dep</code> lines
+entirely if the information in the package index is good enough.
+And committing that file to your project would be the only thing
+needed to lock the dependencies. Of course if a <code>dep</code>
+line is specified this would instead override the file.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_alien_shaman">Alien Shaman</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>This is the two-parts project requested by the LeoFS team.
+This is essentially a "distributed bigwig". I am hoping to
+have a prototype up in a few days.</p></div>
+<div class="paragraph"><p>Alien is the part that allows writing and enabling probes
+in your nodes. Probes send events which may get filtered before
+being forwarded to their destination. The events may be sent
+to a local process, a remote process, over UDP, TCP or SSL.
+Events may also be received by a process called a relay, which
+may be used to group or aggregate data before it is being sent
+over the network, reducing the footprint overall.</p></div>
+<div class="paragraph"><p>Shaman is the UI for it. It will ultimately be able to display
+any event as long as it’s configured to do so. Events may be logs,
+numeric values displayed on graphs updated in real time, lists of
+items like processes and so on.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_feedback">Feedback</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>That’s it for today! There will be another status update once
+Shaman is out. But for now I have to focus on it.</p></div>
+<div class="paragraph"><p>As always, please send feedback on the projects, this post,
+the sponsoring idea, anything really! Thanks.</p></div>
+</div>
+</div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/on-open-source/index.html b/articles/on-open-source/index.html new file mode 100644 index 00000000..55519160 --- /dev/null +++ b/articles/on-open-source/index.html @@ -0,0 +1,276 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: On open source</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>On open source</span></h1> + <p class="date"> + <span class="day">05</span> + <span class="month">Sep</span> + </p> +</header> + +<div class="paragraph"><p>Last week I read a great article
+<a href="http://videlalvaro.github.io/2014/08/on-contributing-to-opensource.html">on
+contributing to open source</a> by Alvaro Videla. He makes
+many great points and I am in agreement with most of it.
+This made me want to properly explain my point of view with
+regard to open source and contributions. Unlike most open
+source evangelism articles I will not talk about ideals or
+any of that crap, but rather my personal feelings and
+experience.</p></div>
+<div class="paragraph"><p>I have been doing open source work for quite some time.
+My very first open source project was a graphics driver
+for (the very early version of) the PCSX2 emulator. That
+was more than ten years ago, and there
+<a href="http://ngemu.com/threads/gstaris-0-6.30469/">isn’t
+much left to look at today</a>. This was followed by a
+<a href="https://github.com/extend/wee">PHP framework</a>
+(started long before Zend Framework was even a thing) and
+a few other small projects. None of them really took off.
+It’s alright, that’s pretty much the fate of most open
+source projects. You spend a lot of work and sweat and
+get very little in return from others.</p></div>
+<div class="paragraph"><p>This sounds harsh but this is the reality of all open
+source projects. If you are thinking of building a project
+and releasing it as open source, you should be prepared
+for that. This is how most of your projects will feel like.
+Don’t release a project as open source thinking everyone
+will pat you on the back and cheer, this won’t happen. In
+fact if your project is a too small improvement over existing
+software, what many people will do is say you have NIH
+syndrome, regardless of the improvement you bring. So you
+need not to rely on other people in order to get your
+enjoyment out of building open source software.</p></div>
+<div class="paragraph"><p>In my case I get enjoyment from thinking about problems
+that need solving. Often times the problems are already
+solved, but nevermind that, I still think about them and
+sometimes come up with something I feel is better and then
+write code for it. Writing code is also fun, but not as
+fun as using my brain to imagine solutions.</p></div>
+<div class="paragraph"><p>You don’t need thousands of users to do that. So are
+users worthless to me then? No, of course not. In fact
+they are an important component: they bring me problems
+that need solving. So users are very important to me.
+But that’s not the only reason.</p></div>
+<div class="paragraph"><p>I got lucky that the Cowboy project became popular.
+And seeing it be this popular, and some of my other projects
+also do quite well, made me believe I could perhaps work
+full time on open source. If I can work full time then
+I can produce better software. What I had one hour to
+work on before I can now spend a day on, and experiment
+until I am satisfied. This is very useful because that
+means I can get it almost right from the beginning, and
+avoid the million API breaking changes that occured
+before Cowboy 1.0 was released.</p></div>
+<div class="paragraph"><p>To be able to work full time on open source however,
+I need money. This is a largely unspoken topic of open
+source work. The work is never free. You can download the
+product for free, but someone has to pay for the work
+itself. Life is unfortunately not free.</p></div>
+<div class="paragraph"><p>Large projects and some lucky people have their work
+sponsored by their employers. Everyone else has to deal
+with it differently. In my case I was sponsored for a
+while by the <a href="http://leo-project.net/leofs/">LeoFS</a>
+project, but that ended. I also had the Farwest fundraiser,
+which was a success, although the project stalled after that.
+(Fear not, as Farwest will make a comeback as a conglomerate
+of Web development projects in the future.) After that I set
+up the <a href="http://ninenines.eu/support/">sponsoring scheme</a>,
+which I can proudly say today brings in enough money to
+cover my food and shelter. Great!</p></div>
+<div class="paragraph"><p>This is a start, but it’s of course not enough. Life
+is a little more than food and shelter, and so I am still
+looking for sponsors. This is not a very glorious experience,
+as I am essentially looking for scraps that companies can
+throw away. Still, if a handful more companies were doing
+that, not only would I be able to live comfortably, but I
+would also be able to stop worrying about the future as I
+could put money on the side for when it gets rough.</p></div>
+<div class="paragraph"><p>A few companies giving me some scrap money so I could
+live and work independently is by far the most important
+thing anyone can do to help my projects, including Cowboy.
+Yes, they’re even more important than code contributions,
+bug reports and feedback. Because this money gives me the
+time I need to handle the code contributions, bug reports
+and feedback.</p></div>
+<div class="paragraph"><p>If Cowboy or another project is a large part of your
+product or infrastructure, then the best thing you can do
+is become a sponsor. The second best is opening tickets
+and/or providing feedback. The third best is providing
+good code contributions.</p></div>
+<div class="paragraph"><p>I will not expand on the feedback part. Feedback is
+very important, and even just a high five or a retweet
+is already good feedback. It’s not very complicated.</p></div>
+<div class="paragraph"><p>I want to expand a little on code contributions
+however. Not long ago I ran across the term "patch bomb"
+which means dropping patches and expecting the project
+maintainers to merge them and maintain them. I receive
+a lot of patches, and often have to refuse them. Causes
+for refusal vary. Some patches only benefit the people
+who submitted them (or a very small number of people).
+Some patches are not refined enough to be included.
+Others are out of scope of the project. These are some
+of the reasons why I refuse patches. Having limited
+time and resources, I have to focus my efforts on the
+code used by the larger number of users. I have to
+prioritize patches from submitters who are reactive
+and address the issues pointed out. And I have to plainly
+refuse other patches.</p></div>
+<div class="paragraph"><p>I believe this wraps up my thoughts on open source.
+Overall I had a great experience, the Erlang community
+being nice and understanding of the issues at hand in
+general. And if the money problem could be solved soon,
+then I would be one of the luckiest and happiest open
+source developer on Earth.</p></div>
+<div class="paragraph"><p>Think about it the next time you see a donation button
+or a request for funds or sponsoring. You can considerably
+improve an open source developer’s life with very little
+of your company’s money.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/page/1/index.html b/articles/page/1/index.html new file mode 100644 index 00000000..91d8267b --- /dev/null +++ b/articles/page/1/index.html @@ -0,0 +1 @@ +<!DOCTYPE html><html><head><link rel="canonical" href="http://ninenines.eu/articles/"/><meta http-equiv="content-type" content="text/html; charset=utf-8" /><meta http-equiv="refresh" content="0;url=http://ninenines.eu/articles/" /></head></html>
\ No newline at end of file diff --git a/articles/ranch-ftp/index.html b/articles/ranch-ftp/index.html new file mode 100644 index 00000000..cd22ee72 --- /dev/null +++ b/articles/ranch-ftp/index.html @@ -0,0 +1,369 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Build an FTP Server with Ranch in 30 Minutes</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Build an FTP Server with Ranch in 30 Minutes</span></h1> + <p class="date"> + <span class="day">14</span> + <span class="month">Nov</span> + </p> +</header> + +<div class="paragraph"><p>Last week I was speaking at the
+<a href="http://www.erlang-factory.com/conference/London2012/speakers/LoicHoguin">London Erlang Factory Lite</a>
+where I presented a live demonstration of building an FTP server using
+<a href="http://ninenines.eu/docs/en/ranch/HEAD/README">Ranch</a>.
+As there was no slide, you should use this article as a reference instead.</p></div>
+<div class="paragraph"><p>The goal of this article is to showcase how to use Ranch for writing
+a network protocol implementation, how Ranch gets out of the way to let
+you write the code that matters, and the common techniques used when
+writing servers.</p></div>
+<div class="paragraph"><p>Let’s start by creating an empty project. Create a new directory and
+then open a terminal into that directory. The first step is to add Ranch
+as a dependency. Create the <code>rebar.config</code> file and add the
+following 3 lines.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #FF6600">deps</span>, [
+ {<span style="color: #FF6600">ranch</span>, <span style="color: #FF0000">".*"</span>, {<span style="color: #FF6600">git</span>, <span style="color: #FF0000">"git://github.com/extend/ranch.git"</span>, <span style="color: #FF0000">"master"</span>}}
+]}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>This makes your application depend on the last Ranch version available
+on the <em>master</em> branch. This is fine for development, however when
+you start pushing your application to production you will want to revisit
+this file to hardcode the exact version you are using, to make sure you
+run the same version of dependencies in production.</p></div>
+<div class="paragraph"><p>You can now fetch the dependencies.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ rebar get-deps
+<span style="color: #990000">==></span> ranch_ftp <span style="color: #990000">(</span>get-deps<span style="color: #990000">)</span>
+Pulling ranch from {git<span style="color: #990000">,</span><span style="color: #FF0000">"git://github.com/extend/ranch.git"</span><span style="color: #990000">,</span><span style="color: #FF0000">"master"</span>}
+Cloning into <span style="color: #FF0000">'ranch'</span><span style="color: #990000">...</span>
+<span style="color: #990000">==></span> ranch <span style="color: #990000">(</span>get-deps<span style="color: #990000">)</span></tt></pre></div></div>
+<div class="paragraph"><p>This will create a <em>deps/</em> folder containing Ranch.</p></div>
+<div class="paragraph"><p>We don’t actually need anything else to write the protocol code.
+We could make an application for it, but this isn’t the purpose of this
+article so let’s just move on to writing the protocol itself. Create
+the file <em>ranch_ftp_protocol.erl</em> and open it in your favorite
+editor.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ vim ranch_ftp_protocol<span style="color: #990000">.</span>erl</tt></pre></div></div>
+<div class="paragraph"><p>Let’s start with a blank protocol module.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000080">-module</span></span>(<span style="color: #FF6600">ranch_ftp_protocol</span>)<span style="color: #990000">.</span>
+<span style="font-weight: bold"><span style="color: #000080">-export</span></span>([<span style="font-weight: bold"><span style="color: #000000">start_link</span></span><span style="color: #990000">/</span><span style="color: #993399">4</span>, <span style="font-weight: bold"><span style="color: #000000">init</span></span><span style="color: #990000">/</span><span style="color: #993399">3</span>])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">start_link</span></span>(<span style="color: #009900">ListenerPid</span>, <span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">Opts</span>) <span style="color: #990000">-></span>
+ <span style="color: #009900">Pid</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000080">spawn_link</span></span>(<span style="font-weight: bold"><span style="color: #000080">?MODULE</span></span>, <span style="color: #FF6600">init</span>, [<span style="color: #009900">ListenerPid</span>, <span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>]),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Pid</span>}<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">ListenerPid</span>, <span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Got a connection!~n"</span>),
+ <span style="color: #FF6600">ok</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>When Ranch receives a connection, it will call the <code>start_link/4</code>
+function with the listener’s pid, socket, transport module to be used,
+and the options we define when starting the listener. We don’t need options
+for the purpose of this article, so we don’t pass them to the process we are
+creating.</p></div>
+<div class="paragraph"><p>Let’s open a shell and start a Ranch listener to begin accepting
+connections. We only need to call one function. You should probably open
+it in another terminal and keep it open for convenience. If you quit
+the shell you will have to repeat the commands to proceed.</p></div>
+<div class="paragraph"><p>Also note that you need to type <code>c(ranch_ftp_protocol).</code>
+to recompile and reload the code for the protocol. You do not need to
+restart any process however.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ erl -pa ebin deps<span style="color: #990000">/*</span>/ebin
+Erlang R15B02 <span style="color: #990000">(</span>erts-<span style="color: #993399">5.9</span><span style="color: #990000">.</span><span style="color: #993399">2</span><span style="color: #990000">)</span> <span style="color: #990000">[</span><span style="font-weight: bold"><span style="color: #0000FF">source</span></span><span style="color: #990000">]</span> <span style="color: #990000">[</span><span style="color: #993399">64</span>-bit<span style="color: #990000">]</span> <span style="color: #990000">[</span>smp<span style="color: #990000">:</span><span style="color: #993399">4</span><span style="color: #990000">:</span><span style="color: #993399">4</span><span style="color: #990000">]</span> <span style="color: #990000">[</span>async-threads<span style="color: #990000">:</span><span style="color: #993399">0</span><span style="color: #990000">]</span> <span style="color: #990000">[</span>hipe<span style="color: #990000">]</span> <span style="color: #990000">[</span>kernel-poll<span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #0000FF">false</span></span><span style="color: #990000">]</span>
+
+Eshell V5<span style="color: #990000">.</span><span style="color: #993399">9.2</span> <span style="color: #990000">(</span>abort with <span style="color: #990000">^</span>G<span style="color: #990000">)</span></tt></pre></div></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">1</span><span style="color: #990000">></span> <span style="font-weight: bold"><span style="color: #000000">application:start</span></span>(<span style="color: #FF6600">ranch</span>)<span style="color: #990000">.</span>
+<span style="color: #FF6600">ok</span>
+<span style="color: #993399">2</span><span style="color: #990000">></span> <span style="font-weight: bold"><span style="color: #000000">ranch:start_listener</span></span>(<span style="color: #FF6600">my_ftp</span>, <span style="color: #993399">10</span>,
+ <span style="color: #FF6600">ranch_tcp</span>, [{<span style="color: #FF6600">port</span>, <span style="color: #993399">2121</span>}],
+ <span style="color: #FF6600">ranch_ftp_protocol</span>, [])<span style="color: #990000">.</span>
+{<span style="color: #FF6600">ok</span>,<span style="color: #990000"><</span><span style="color: #993399">0.40</span><span style="color: #990000">.</span><span style="color: #993399">0</span><span style="color: #990000">></span>}</tt></pre></div></div>
+<div class="paragraph"><p>This starts a listener named <code>my_ftp</code> that runs your very own
+<code>ranch_ftp_protocol</code> over TCP, listening on port <code>2121</code>.
+The last argument is the options given to the protocol that we ignored
+earlier.</p></div>
+<div class="paragraph"><p>To try your code, you can use the following command. It should be able
+to connect, the server will print a message in the console, and then
+the client will print an error.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ ftp localhost <span style="color: #993399">2121</span></tt></pre></div></div>
+<div class="paragraph"><p>Let’s move on to actually writing the protocol.</p></div>
+<div class="paragraph"><p>Once you have created the new process and returned the pid, Ranch will
+give ownership of the socket to you. This requires a synchronization
+step though.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">ListenerPid</span>, <span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
+ <span style="color: #0000FF">ok</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">ranch:accept_ack</span></span>(<span style="color: #009900">ListenerPid</span>),
+ <span style="color: #FF6600">ok</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Now that you acknowledged the new connection, you can use it safely.</p></div>
+<div class="paragraph"><p>When an FTP server accepts a connection, it starts by sending a
+welcome message which can be one or more lines starting with the
+code <code>200</code>. Then the server will wait for the client
+to authenticate the user, and if the authentication went successfully,
+which it will always do for the purpose of this article, it will reply
+with a <code>230</code> code.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">init</span></span>(<span style="color: #009900">ListenerPid</span>, <span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
+ <span style="color: #0000FF">ok</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">ranch:accept_ack</span></span>(<span style="color: #009900">ListenerPid</span>),
+ <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">send</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"200 My cool FTP server welcomes you!\r\n"</span><span style="color: #990000">>></span>),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Data</span>} <span style="color: #990000">=</span> <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">recv</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #993399">0</span>, <span style="color: #993399">30000</span>),
+ <span style="font-weight: bold"><span style="color: #000000">auth</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">Data</span>)<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">auth</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"USER "</span>, <span style="color: #009900">Rest</span><span style="color: #990000">/</span><span style="color: #FF6600">bits</span><span style="color: #990000">>></span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"User authenticated! ~p~n"</span>, [<span style="color: #009900">Rest</span>]),
+ <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">send</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"230 Auth OK\r\n"</span><span style="color: #990000">>></span>),
+ <span style="color: #FF6600">ok</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>As you can see we don’t need complex parsing code. We can simply
+match on the binary in the argument!</p></div>
+<div class="paragraph"><p>Next we need to loop receiving data commands and optionally
+execute them, if we want our server to become useful.</p></div>
+<div class="paragraph"><p>We will replace the <code>ok.</code> line with the call to
+the following function. The new function is recursive, each call
+receiving data from the socket and sending a response. For now
+we will send an error response for all commands the client sends.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">loop</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">recv</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #993399">0</span>, <span style="color: #993399">30000</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Data</span>} <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">Data</span>),
+ <span style="font-weight: bold"><span style="color: #000000">loop</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>);
+ {<span style="color: #FF6600">error</span>, <span style="color: #990000">_</span>} <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"The client disconnected~n"</span>)
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">Data</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Command received ~p~n"</span>, [<span style="color: #009900">Data</span>]),
+ <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">send</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"500 Bad command\r\n"</span><span style="color: #990000">>></span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>With this we are almost ready to start implementing commands.
+But with code like this we might have errors if the client doesn’t
+send just one command per packet, or if the packets arrive too fast,
+or if a command is split over multiple packets.</p></div>
+<div class="paragraph"><p>To solve this, we need to use a buffer. Each time we receive data,
+we will append to the buffer, and then check if we have received a
+command fully before running it. The code could look similar to the
+following.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">loop</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">Buffer</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="color: #009900">Transport</span><span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #000000">recv</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #993399">0</span>, <span style="color: #993399">30000</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Data</span>} <span style="color: #990000">-></span>
+ <span style="color: #009900">Buffer2</span> <span style="color: #990000">=</span> <span style="color: #990000"><<</span> <span style="color: #009900">Buffer</span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000080">binary</span></span>, <span style="color: #009900">Data</span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000080">binary</span></span> <span style="color: #990000">>></span>,
+ {<span style="color: #009900">Commands</span>, <span style="color: #009900">Rest</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">split</span></span>(<span style="color: #009900">Buffer2</span>),
+ [<span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>, <span style="color: #009900">C</span>) || <span style="color: #009900">C</span> <span style="color: #990000"><-</span> <span style="color: #009900">Commands</span>],
+ <span style="font-weight: bold"><span style="color: #000000">loop</span></span>(<span style="color: #009900">Socket</span>, <span style="color: #009900">Transport</span>);
+ {<span style="color: #FF6600">error</span>, <span style="color: #990000">_</span>} <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"The client disconnected~n"</span>)
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The implementation of <code>split/1</code> is left as an exercice
+to the reader. You will also probably want to handle the <code>QUIT</code>
+command, which must stop any processing and close the connection.</p></div>
+<div class="paragraph"><p>The attentive reader will also take note that in the case of text-
+based protocols where commands are separated by line breaks, you can
+set an option using <code>Transport:setopts/2</code> and have all the
+buffering done for you for free by Erlang itself.</p></div>
+<div class="paragraph"><p>As you can surely notice by now, Ranch allows us to build network
+applications by getting out of our way entirely past the initial setup.
+It lets you use the power of binary pattern matching to write text and
+binary protocol implementations in just a few lines of code.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="http://www.erlang-factory.com/conference/London2012/speakers/LoicHoguin">Watch the talk</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/the-story-so-far/index.html 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src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>The story so far</span></h1> + <p class="date"> + <span class="day">23</span> + <span class="month">Aug</span> + </p> +</header> + +<div class="paragraph"><p>As I am away from home with little to do (some call this
+a vacation) I wanted to reflect a little on the story so far,
+or how I arrived to Erlang and got to where I am now. The
+raw personal experience. It’ll be an article that’s more
+about social aspect, communities and marketing a project than
+technical considerations. As a period piece, it will also
+allow me to reflect on the evolution of Erlang in recent
+years.</p></div>
+<div class="paragraph"><p>Once upon a time-- Okay this isn’t a fairy tale. The story
+begins with a short chapter in 2010. The year 2010 started
+with a fairly major event in my life: the US servers for the
+online game I stopped playing a few months before, but was
+still involved with through its community, were closing. OMG!
+Someone found a way to log packets and started working on a
+private server; meanwhile the JP servers were still up. And
+that’s pretty much it.</p></div>
+<div class="paragraph"><p>Fast forward a few months and it became pretty clear that
+the private server was going nowhere considering all the drama
+surrounding it-- which is actually not unusual, but it was
+more entertaining than average and the technical abilities of
+people running the project were obviously lacking so I decided
+to obtain those logged packets and look at things myself. I
+didn’t want to do a private server yet, I only wanted to take
+a peek to see how things worked, and perhaps organize some
+effort to document the protocol.</p></div>
+<div class="paragraph"><p>There was 10GB of logs. I didn’t have an easy to use
+language to analyze them, and hex editors wouldn’t cut it for
+most purposes, so I had to look elsewhere. This was a good
+opportunity to start learning this PHP killer I read about
+before, which also happens to feature syntax for matching
+binaries, called Erlang. To be perfectly honest I wouldn’t
+have touched the logs if I didn’t have the added motivation
+to play with and learn a new language.</p></div>
+<div class="paragraph"><p>At the time it was pretty hard to learn Erlang. In my
+experience there was Joe’s book (which I always recommend
+first as I believe it is the best to learn the Erlang side
+of things; but falls a little short on OTP), and there was
+about 5 chapters of LYSE. There were a couple other books
+I never managed to get into (sorry guys), and there was also
+a few interesting blogs, some of which I can’t find anymore.
+Finally the #erlang IRC community was there but I was strictly
+lurking at the time.</p></div>
+<div class="paragraph"><p>What a difference compared to 4 years later! (That’s
+today, by the way!) Now we have more books than I can
+remember, tons of articles covering various aspects of the
+language and platform, many targeting beginners but a good
+number of them also about advanced topics. We even have a
+free online book, LYSE, with more than 30 chapters covering
+pretty much everything. Needless to say I never finished
+reading LYSE as it got written slower than I learnt.</p></div>
+<div class="paragraph"><p>Back to 2010. I wrote a parser for the logs, and
+aggregated those results into one CSV file per packet type
+so I could open them in Gnumeric and aggregate some more,
+but manually this time, and draw conclusions on the packet
+structures. That was pretty easy. Even for a beginner.
+Anyone can go from zero to that level in a day or two.
+Then, having mastered binary pattern matching, I wanted
+to learn some more Erlang, by making this aggregation
+faster. What I had done before worked, but I wasn’t going
+to wait forever to process everything sequentially. So I
+looked and found a project called <code>plists</code> (still exists,
+but not maintained AFAIK). I downloaded that project and
+replaced my <code>lists:</code> calls to <code>plists:</code>.
+Boom. In just a few minutes all logs were processed, and
+I had learnt something new.</p></div>
+<div class="paragraph"><p>It is particularly interesting to note that the lack of
+a package manager or index never bothered me. Neither before
+nor after learning Erlang. My experience with package
+managers was mostly related to Ubuntu, a little Perl and
+Python, and PHP’s Pear. Let’s just stay polite and say it
+was always a terrible experience. So searching on the Web
+didn’t feel awkward, because even if I used a tool or
+website I would have ended up doing a search or two anyway.
+This is in contrast to the package index feature in
+<a href="https://github.com/ninenines/erlang.mk">Erlang.mk</a>,
+which is meant to simplify specifying dependencies more
+than anything: <code>DEPS = cowboy</code>. It does not
+attempt to solve any other problem, and will only attempt
+to solve one extra problem in the near future, which is
+the discovery of packages. So expect some kind of website
+listing packages soon enough.</p></div>
+<div class="paragraph"><p>I want to use this parenthese to also point out that at
+the time there was a very small number of projects out there,
+at least compared to today. While you sometimes hear people
+complain about lack of certain libraries, it is so much
+better now than it was before! The situation improves very
+quickly, so much that it’s not going to be that big an issue
+soon enough.</p></div>
+<div class="paragraph"><p>Wanting to know more about that game’s protocol, in the
+year 2010, I ended up starting to write more Erlang code to
+simulate a server and use the server to query the client and
+see what was happening, documenting the packets and so on.
+This eventually lead to a larger project implementing more
+and more until people got their hopes up for a revival of
+the game, all the while the now competing original server
+project died in a stream of drama and technical incompetence.
+Of course, I ended up doing what any good Internet citizen
+would do, I crushed people’s hopes, but that’s not important
+to our story. The important part is that before giving up
+on this project, I not only learnt a good deal of Erlang
+and a little deal of OTP (which I did not touch until 6
+months after I started with Erlang; see the paragraph
+about learning material above), but I also had an intriguing
+idea pop into my mind for what would become my greatest
+success yet.</p></div>
+<div class="paragraph"><p>The giving up part was not easy. Having had financial
+difficulties all year 2010 and part of 2009, I resolved
+to travel back to Paris to try and make it. I ended up
+sleeping in offices for 6 months, being hosted by a shady
+person, and hearing my fair share of stories about
+the dark side of business. While there I also worked for
+another company with someone who would end up becoming
+another high profile Erlang developer. The situation
+slowly improved, I started taking part in the #erlang
+IRC discussions, giving up my status of lurker and, a
+few months into 2011, started working on the Apache killer
+project: Cowboy.</p></div>
+<div class="paragraph"><p>This is the part where I probably should get accused of
+racism and other fun things, but I never did. And I think
+that speaks lots about the Erlang community. In all my time
+writing Erlang code, I can count the number of conflicts I
+had with other people on a single hand. This is the nicest
+programming community I have ever seen, by far. And the
+humblest too. The Erlang community feels like Japan. And
+I love Japan. So I love the Erlang community. I can’t say
+this enough. This is something that stayed true for all
+my time using Erlang, and despite the rise of alternative
+languages that are not Japan the Erlang community has
+remained very Japan.</p></div>
+<div class="paragraph"><p>The first published version of Cowboy was written in
+two weeks. A little before those two weeks, during, and
+a while after, pretty much everything I said on the
+Internets was that Cowboy was going to be the greatest
+HTTP server ever, that the other servers were problematic
+(and just to be clear, Yaws was rarely if ever mentioned,
+due to being in a perceived different league of "full
+featured servers" while Cowboy was a "lightweight server"),
+and that Cowboy will be the best replacement to a Mochiweb
+or Misultin application. This, alongside a lot of time
+spent on IRC telling people to use Cowboy when they were
+asking for an HTTP server to use, probably made me sound
+very annoying. But it worked, and Cowboy started getting
+its first users, despite being only a few weeks old. Of
+course, as soon as I got my very first user, I started
+claiming Cowboy had "a lot of users".</p></div>
+<div class="paragraph"><p>Looking back today I would definitely find myself annoying,
+this wasn’t just an idle comment there. For about a year,
+maybe a little more, all I ever said was that Cowboy was
+the best. This probably made me a little dumber in the
+process (as if I wasn’t enough! I know). Being French, I
+sometimes would also say things quite abruptly. To stay
+polite, I probably sounded like an asshole. I learnt to
+stop being so French over time thankfully.</p></div>
+<div class="paragraph"><p>I think what was most important to Cowboy at the time,
+was three things. First, it felt fresh. It was new, had new
+ideas, tried to do things differently and followed "new" old
+best practices (the OTP way-- which was simply too obscure
+for most people at the time). Second, it had me spending
+all my time telling people to use it whenever they were
+looking for an HTTP server. Third, it had me helping people
+get started with it and guide them all the steps of the way.
+Mostly because it didn’t have a very good documentation, but
+still, hand holding does wonders.</p></div>
+<div class="paragraph"><p>To be able to help people every time they had a problem,
+I did not spend all my days reading IRC. Instead I simply
+made sure to be notified when someone said <code>cowboy</code>.
+The same way many people subscribe to alerts when their
+company is mentioned in the news. Nothing fancy.</p></div>
+<div class="paragraph"><p>Time went on, Cowboy grew, or as some like to say,
+completely destroyed the competition, and many people
+eventually moved from Mochiweb and Misultin to Cowboy.
+And then Roberto Ostinelli stopped Misultin development
+and told everyone to move to Cowboy. This is the most
+humble and selfless act I have ever seen in the programming
+sphere, and I only have one thing to say about it: GG.
+Thanks for the fish. He left me with the tasks of improving
+Cowboy examples, documentation and strongly believed that
+the Misultin interface was more user friendly out of all
+the servers. So I added many examples, as many lines of
+documentation as we have of code, and strongly believe
+that Cowboy 2.0 will be the most user friendly interface
+out of all servers. But only time will tell.</p></div>
+<div class="paragraph"><p>With the rise of the project and the rise in the number
+of users, my previous strategy (completely incidental, by
+the way, and definitely not a well thought out plan to
+become popular) stopped working. It was taking me too much
+time. The important aspects slowly drifted. If I wanted to
+support more users, I would have to spend less time with
+each individual user. This was actually a hard problem.
+You basically have to make people understand they can’t
+just come to you directly when they have a problem, they
+have to follow proper channels. It becomes less personal,
+and might be felt like you don’t care about them anymore.
+You have to hurt some people’s feelings at this point. It
+is quite unfortunate, and also quite difficult to do. There
+is some unwritten rule that says early adopters deserve
+more, but in the real world it never works like this. So
+I probably hurt some people’s feelings at some point. But
+that’s okay. Because even if you make sure to be as nice
+as possible when you tell people to go through proper
+channels from now on, some people will still get offended.
+There’s nothing you can do about it.</p></div>
+<div class="paragraph"><p>From that point onward the important points about the
+project was getting the documentation done, making sure
+people knew about the proper channels to get help and
+report issues, etc. Basically making myself less needed.
+This is quite a contrast with the first days, but I believe
+Cowboy made that transition successfully.</p></div>
+<div class="paragraph"><p>Not only did I win time by not having to hold hands with
+everyone all the time (not that I didn’t like it, but you
+know, the sweat), but I also won time thanks to the increased
+project popularity. Indeed, the more users you have, the more
+annoying guys there are to tell people to use your project
+and that it’s the best and everything. Which is great. At
+least, it’s great if you don’t pay too much attention to it.
+Sometimes people will give an advice that is, in your opinion,
+a bad advice. And that’s okay. Don’t intervene every time
+someone gives a bad advice, learn to let it go. People will
+figure it out. You learn by making mistakes, after all. Use
+this extra time to make sure other people don’t end up
+giving the same bad advice instead. Fix the code or the
+documentation that led to this mistake. Slowly improve the
+project and make sure it doesn’t happen again.</p></div>
+<div class="paragraph"><p>This is my story. So far, anyway.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/tictactoe/index.html b/articles/tictactoe/index.html new file mode 100644 index 00000000..9eab4520 --- /dev/null +++ b/articles/tictactoe/index.html @@ -0,0 +1,242 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Erlang Tic Tac Toe</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Erlang Tic Tac Toe</span></h1> + <p class="date"> + <span class="day">17</span> + <span class="month">Oct</span> + </p> +</header> + +<div class="paragraph"><p>Everyone knows <a href="http://en.wikipedia.org/wiki/Tic-tac-toe">Tic Tac Toe</a>,
+right?</p></div>
+<div class="paragraph"><p>Players choose either to be the Xs or the Os, then place their symbol
+on a 3x3 board one after another, trying to create a line of 3 of them.</p></div>
+<div class="paragraph"><p>Writing an algorithm to check for victory sounds easy, right? It’s
+easily tested, considering there’s only 8 possible winning rows (3 horizontal,
+3 vertical and 2 diagonal).</p></div>
+<div class="paragraph"><p>In Erlang though, you probably wouldn’t want an algorithm. Erlang has
+this cool feature called pattern matching which will allow us to completely
+avoid writing the algorithm by instead letting us match directly on the
+solutions.</p></div>
+<div class="paragraph"><p>Let’s first create a board. A board is a list of 3 rows each containing
+3 columns. It can also be thought of as a tuple containing 9 elements.
+A tuple is easier to manipulate so this is what we are going to use.
+Each position can either contain an <code>x</code>, an <code>o</code>,
+or be <code>undefined</code>.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">new</span></span>() <span style="color: #990000">-></span>
+ {<span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>,
+ <span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>,
+ <span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>, <span style="color: #000080">undefined</span>}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Now that we have a board, if we want to play, we need a function that
+will allow players to, you know, actually play their moves. Rows and
+columns are numbered 1 to 3 so we need a little math to correctly
+deduce the element’s position.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">play</span></span>(<span style="color: #009900">Who</span>, <span style="color: #009900">X</span>, <span style="color: #009900">Y</span>, <span style="color: #009900">Board</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">setelement</span></span>((<span style="color: #009900">Y</span> <span style="color: #990000">-</span> <span style="color: #993399">1</span>) <span style="color: #990000">*</span> <span style="color: #993399">3</span> <span style="color: #990000">+</span> <span style="color: #009900">X</span>, <span style="color: #009900">Board</span>, <span style="color: #009900">Who</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>This function returns the board with the element modified. Of course,
+as you probably noticed, we aren’t checking that the arguments are correct,
+or that the element was already set. This is left as an exercise to the
+reader.</p></div>
+<div class="paragraph"><p>After playing the move, we need to check whether someone won. That’s
+where you’d write an algorithm, and that’s where I wouldn’t. Let’s just
+pattern match all of them!</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">check</span></span>(<span style="color: #009900">Board</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="color: #009900">Board</span> <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ {<span style="color: #FF6600">x</span>, <span style="color: #FF6600">x</span>, <span style="color: #FF6600">x</span>,
+ <span style="color: #990000">_</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>,
+ <span style="color: #990000">_</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>} <span style="color: #990000">-></span> {<span style="color: #FF6600">victory</span>, <span style="color: #FF6600">x</span>};
+
+ {<span style="color: #FF6600">x</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>,
+ <span style="color: #990000">_</span>, <span style="color: #FF6600">x</span>, <span style="color: #990000">_</span>,
+ <span style="color: #990000">_</span>, <span style="color: #990000">_</span>, <span style="color: #FF6600">x</span>} <span style="color: #990000">-></span> {<span style="color: #FF6600">victory</span>, <span style="color: #FF6600">x</span>};
+
+ {<span style="color: #FF6600">x</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>,
+ <span style="color: #FF6600">x</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>,
+ <span style="color: #FF6600">x</span>, <span style="color: #990000">_</span>, <span style="color: #990000">_</span>} <span style="color: #990000">-></span> {<span style="color: #FF6600">victory</span>, <span style="color: #FF6600">x</span>};
+
+ <span style="font-style: italic"><span style="color: #9A1900">%% [snip]</span></span>
+
+ <span style="color: #990000">_</span> <span style="color: #990000">-></span> <span style="color: #FF6600">ok</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Pattern matching allows us to simply <em>draw</em> the solutions
+directly inside our code, and if the board matches any of them, then we
+have a victory or a draw, otherwise the game can continue.</p></div>
+<div class="paragraph"><p>The <code>_</code> variable is special in that it always matches,
+allowing us to focus strictly on the winning row. And because it’s very
+graphical, if we were to have messed up somewhere, then we’d only need
+take a quick glance to be sure the winning solutions are the right ones.</p></div>
+<div class="paragraph"><p>Erlang allows us to transform algorithms into very graphical code thanks
+to its pattern matching feature, and let us focus on doing things instead
+of writing algorithms to do things.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="/res/tictactoe.erl">tictactoe.erl</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/xerl-0.1-empty-modules/index.html b/articles/xerl-0.1-empty-modules/index.html new file mode 100644 index 00000000..bbda8b40 --- /dev/null +++ b/articles/xerl-0.1-empty-modules/index.html @@ -0,0 +1,297 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Xerl: empty modules</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link 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href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Xerl: empty modules</span></h1> + <p class="date"> + <span class="day">30</span> + <span class="month">Jan</span> + </p> +</header> + +<div class="paragraph"><p>Let’s build a programming language. I call it Xerl: eXtended ERLang.
+It’ll be an occasion for us to learn a few things, especially me.</p></div>
+<div class="paragraph"><p>Unlike in Erlang, in this language, everything is an expression.
+This means that modules and functions are expression, and indeed that
+you can have more than one module per file.</p></div>
+<div class="paragraph"><p>We are just starting, so let’s no go ahead of ourselves here. We’ll
+begin with writing the code allowing us to compile an empty module.</p></div>
+<div class="paragraph"><p>We will compile to Core Erlang: this is one of the many intermediate
+step your Erlang code compiles to before it becomes BEAM machine code.
+Core Erlang is a very neat language for machine generated code, and we
+will learn many things about it.</p></div>
+<div class="paragraph"><p>Today we will only focus on compiling the following code:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">my_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Compilation will be done in a few steps. First, the source file will
+be transformed in a tree of tokens by the lexer. Then, the parser will
+use that tree of tokens and convert it to the AST, bringing semantical
+meaning to our representation. Finally, the code generator will transform
+this AST to Core Erlang AST, which will then be compiled.</p></div>
+<div class="paragraph"><p>We will use <em>leex</em> for the lexer. This lexer uses .xrl files
+which are then compiled to .erl files that you can then compile to BEAM.
+The file is divided in three parts: definitions, rules and Erlang code.
+Definitions and Erlang code are obvious; rules are what concerns us.</p></div>
+<div class="paragraph"><p>We only need two things: atoms and whitespaces. Atoms are a lowercase
+letter followed by any letter, number, _ or @. Whitespace is either a
+space, an horizontal tab, \r or \n. There exists other kinds of whitespaces
+but we simply do not allow them in the Xerl language.</p></div>
+<div class="paragraph"><p>Rules consist of a regular expression followed by Erlang code. The
+latter must return a token representation or the atom <code>skip_token</code>.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #009900">L</span>}{<span style="color: #009900">A</span>}<span style="color: #990000">*</span> <span style="color: #990000">:</span>
+ <span style="color: #009900">Atom</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000080">list_to_atom</span></span>(<span style="color: #009900">TokenChars</span>),
+ {<span style="color: #FF6600">token</span>, <span style="font-weight: bold"><span style="color: #0000FF">case</span></span> <span style="font-weight: bold"><span style="color: #000000">reserved_word</span></span>(<span style="color: #009900">Atom</span>) <span style="font-weight: bold"><span style="color: #0000FF">of</span></span>
+ <span style="color: #000080">true</span> <span style="color: #990000">-></span> {<span style="color: #009900">Atom</span>, <span style="color: #009900">TokenLine</span>};
+ <span style="color: #000080">false</span> <span style="color: #990000">-></span> {<span style="font-weight: bold"><span style="color: #000080">atom</span></span>, <span style="color: #009900">TokenLine</span>, <span style="color: #009900">Atom</span>}
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>}<span style="color: #990000">.</span>
+
+{<span style="color: #009900">WS</span>}<span style="color: #990000">+</span> <span style="color: #990000">:</span> <span style="color: #FF6600">skip_token</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>The first rule matches an atom, which is converted to either a special
+representation for reserved words, or an atom tuple. The
+<code>TokenChars</code> variable represents the match as a string, and
+the <code>TokenLine</code> variable contains the line number.
+<a href="https://github.com/extend/xerl/blob/0.1/src/xerl_lexer.xrl">View the complete file</a>.</p></div>
+<div class="paragraph"><p>We obtain the following result from the lexer:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="color: #FF6600">mod</span>,<span style="color: #993399">1</span>},{<span style="font-weight: bold"><span style="color: #000080">atom</span></span>,<span style="color: #993399">1</span>,<span style="color: #FF6600">my_module</span>},{<span style="color: #FF6600">'begin'</span>,<span style="color: #993399">2</span>},{<span style="color: #FF6600">'end'</span>,<span style="color: #993399">3</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>The second step is to parse this list of tokens to add semantic meaning
+and generate what is called an <em>abstract syntax tree</em>. We will be
+using the <em>yecc</em> parser generator for this. This time it will take
+.yrl files but the process is the same as before. The file is a little
+more complex than for the lexer, we need to define at the very least
+terminals, nonterminals and root symbols, the grammar itself, and
+optionally some Erlang code.</p></div>
+<div class="paragraph"><p>To compile our module, we need a few things. First, everything is an
+expression. We thus need list of expressions and individual expressions.
+We will support a single expression for now, the <code>mod</code>
+expression which defines a module. And that’s it! We end up with the
+following grammar:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$2'</span>]<span style="color: #990000">.</span>
+
+<span style="color: #FF6600">expr</span> <span style="color: #990000">-></span> <span style="color: #FF6600">module</span> <span style="color: #990000">:</span> <span style="color: #FF6600">'$1'</span><span style="color: #990000">.</span>
+
+<span style="color: #FF6600">module</span> <span style="color: #990000">-></span> <span style="color: #FF6600">'mod'</span> <span style="font-weight: bold"><span style="color: #000080">atom</span></span> <span style="color: #FF6600">'begin'</span> <span style="color: #FF6600">'end'</span> <span style="color: #990000">:</span>
+ {<span style="color: #FF6600">'mod'</span>, <span style="font-weight: bold"><span style="color: #000080">?line</span></span>(<span style="color: #FF6600">'$1'</span>), <span style="color: #FF6600">'$2'</span>, []}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p><a href="https://github.com/extend/xerl/blob/0.1/src/xerl_parser.yrl">View the complete file</a>.</p></div>
+<div class="paragraph"><p>We obtain the following result from the parser:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="color: #FF6600">mod</span>,<span style="color: #993399">1</span>,{<span style="font-weight: bold"><span style="color: #000080">atom</span></span>,<span style="color: #993399">1</span>,<span style="color: #FF6600">my_module</span>},[]}]</tt></pre></div></div>
+<div class="paragraph"><p>We obtain a list of a single <code>mod</code> expression. Just like
+we wanted. Last step is generating the Core Erlang code from it.</p></div>
+<div class="paragraph"><p>Code generation generally is comprised of several steps. We will
+discuss these in more details later on. For now, we will focus on the
+minimal needed for successful compilation.</p></div>
+<div class="paragraph"><p>We can use the <code>cerl</code> module to generate Core Erlang AST.
+We will simply be using functions, which allows us to avoid learning
+and keeping up to date with the internal representation.</p></div>
+<div class="paragraph"><p>There’s one important thing to do when generating Core Erlang AST
+for a module: create the <code>module_info/{0,1}</code> functions.
+Indeed, these are added to Erlang before it becomes Core Erlang, and
+so we need to replicate this ourselves. Do not be concerned however,
+as this only takes a few lines of extra code.</p></div>
+<div class="paragraph"><p>As you can see by
+<a href="https://github.com/extend/xerl/blob/0.1/src/xerl_codegen.erl">looking at the complete file</a>,
+the code generator echoes the grammar we defined in the parser, and
+simply applies the appropriate Core Erlang functions for each expressions.</p></div>
+<div class="paragraph"><p>We obtain the following pretty-printed Core Erlang generated code:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'my_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'empty_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'empty_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>For convenience I added all the steps in a <code>xerl:compile/1</code>
+function that you can use against your own .xerl files.</p></div>
+<div class="paragraph"><p>That’s it for today! We will go into more details over each steps in
+the next few articles.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.1/">View the source</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/xerl-0.2-two-modules/index.html b/articles/xerl-0.2-two-modules/index.html new file mode 100644 index 00000000..49ed4702 --- /dev/null +++ b/articles/xerl-0.2-two-modules/index.html @@ -0,0 +1,302 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Xerl: two modules</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link 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href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Xerl: two modules</span></h1> + <p class="date"> + <span class="day">03</span> + <span class="month">Feb</span> + </p> +</header> + +<div class="paragraph"><p>Everything is an expression.</p></div>
+<div class="paragraph"><p>This sentence carries profound meaning. We will invoke it many
+times over the course of these articles.</p></div>
+<div class="paragraph"><p>If everything is an expression, then the language shouldn’t have
+any problem with me defining two modules in the same source file.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">first_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+
+<span style="color: #FF6600">mod</span> <span style="color: #FF6600">second_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Likewise, it shouldn’t have any problem with me defining a
+module inside another module.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">mod</span> <span style="color: #FF6600">out_module</span>
+<span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+ <span style="color: #FF6600">mod</span> <span style="color: #FF6600">in_module</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">begin</span></span>
+ <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Of course, in the context of the Erlang VM, these two snippets
+are equivalent; there is nothing preventing you from calling the
+<code>in_module</code> module from any other module. The <code>mod</code>
+instruction means a module should be created in the Erlang VM,
+with no concept of scope attached.</p></div>
+<div class="paragraph"><p>Still we need to handle both. To do this we will add a step
+between the parser and the code generator that will walk over the
+abstract syntax tree, from here onward shortened as <em>AST</em>,
+and transform the AST by executing it where applicable.</p></div>
+<div class="paragraph"><p>What happens when you execute a <code>mod</code> instruction?
+A module is created. Since we are compiling, that simply means
+the compiler will branch out and create a module.</p></div>
+<div class="paragraph"><p>If everything is an expression, does that mean this will allow
+me to create modules at runtime using the same syntax? Yes, but
+let’s not get ahead of ourselves yet.</p></div>
+<div class="paragraph"><p>For now we will just iterate over the AST, and will compile
+a module for each <code>mod</code> found. Modules cannot contain
+expressions yet, so there’s no need to recurse over it at this
+point. This should solve the compilation of our first snippet.</p></div>
+<div class="paragraph"><p>The <code>compile/1</code> function becomes:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">compile</span></span>(<span style="color: #009900">Filename</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Compiling ~s...~n"</span>, [<span style="color: #009900">Filename</span>]),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Src</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">file:read_file</span></span>(<span style="color: #009900">Filename</span>),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Tokens</span>, <span style="color: #990000">_</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_lexer:string</span></span>(<span style="font-weight: bold"><span style="color: #000080">binary_to_list</span></span>(<span style="color: #009900">Src</span>)),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Exprs</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_parser:parse</span></span>(<span style="color: #009900">Tokens</span>),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Exprs</span>, [])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #990000">_</span>, [], <span style="color: #009900">Modules</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"Done...~n"</span>),
+ {<span style="color: #FF6600">ok</span>, <span style="font-weight: bold"><span style="color: #000000">lists:reverse</span></span>(<span style="color: #009900">Modules</span>)};
+<span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, [<span style="color: #009900">Expr</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">mod</span>, <span style="color: #990000">_</span>, {<span style="font-weight: bold"><span style="color: #000080">atom</span></span>, <span style="color: #990000">_</span>, <span style="color: #009900">Name</span>}, []}|<span style="color: #009900">Tail</span>], <span style="color: #009900">Modules</span>) <span style="color: #990000">-></span>
+ {<span style="color: #FF6600">ok</span>, [<span style="color: #009900">Core</span>]} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">xerl_codegen:exprs</span></span>([<span style="color: #009900">Expr</span>]),
+ {<span style="color: #FF6600">ok</span>, [{<span style="color: #009900">Name</span>, []}]} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">core_lint:module</span></span>(<span style="color: #009900">Core</span>),
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"~s~n"</span>, [<span style="font-weight: bold"><span style="color: #000000">core_pp:format</span></span>(<span style="color: #009900">Core</span>)]),
+ {<span style="color: #FF6600">ok</span>, <span style="color: #990000">_</span>, <span style="color: #009900">Beam</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">compile:forms</span></span>(<span style="color: #009900">Core</span>,
+ [<span style="font-weight: bold"><span style="color: #000080">binary</span></span>, <span style="color: #FF6600">from_core</span>, <span style="color: #FF6600">return_errors</span>, {<span style="color: #FF6600">source</span>, <span style="color: #009900">Filename</span>}]),
+ {<span style="color: #FF6600">module</span>, <span style="color: #009900">Name</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">code:load_binary</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Filename</span>, <span style="color: #009900">Beam</span>),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Tail</span>, [<span style="color: #009900">Name</span>|<span style="color: #009900">Modules</span>])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Running this compiler over the first snippet yields the following
+result:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Compiling</span> <span style="font-weight: bold"><span style="color: #000000">test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span><span style="color: #990000">...</span>
+<span style="color: #FF6600">module</span> <span style="color: #FF6600">'first_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'first_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'first_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="color: #FF6600">module</span> <span style="color: #FF6600">'second_module'</span> [<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>,
+ <span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'second_module'</span>)
+<span style="color: #FF6600">'module_info'</span><span style="color: #990000">/</span><span style="color: #993399">1</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> (<span style="color: #009900">Key</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000080">call</span></span> <span style="color: #FF6600">'erlang'</span><span style="color: #990000">:</span><span style="color: #FF6600">'get_module_info'</span>
+ (<span style="color: #FF6600">'second_module'</span>, <span style="color: #009900">Key</span>)
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
+<span style="color: #009900">Done</span><span style="color: #990000">...</span>
+{<span style="color: #FF6600">ok</span>,[<span style="color: #FF6600">first_module</span>,<span style="color: #FF6600">second_module</span>]}</tt></pre></div></div>
+<div class="paragraph"><p>Everything looks fine. And we can check that the two modules have
+been loaded into the VM:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">9</span><span style="color: #990000">></span> <span style="color: #FF6600">m</span>(<span style="color: #FF6600">first_module</span>)<span style="color: #990000">.</span>
+<span style="color: #009900">Module</span> <span style="color: #FF6600">first_module</span> <span style="color: #FF6600">compiled</span><span style="color: #990000">:</span> <span style="color: #009900">Date</span><span style="color: #990000">:</span> <span style="color: #009900">February</span> <span style="color: #993399">2</span> <span style="color: #993399">2013</span>, <span style="color: #009900">Time</span><span style="color: #990000">:</span> <span style="color: #993399">14.56</span>
+<span style="color: #009900">Compiler</span> <span style="color: #FF6600">options</span><span style="color: #990000">:</span> [<span style="color: #FF6600">from_core</span>]
+<span style="color: #009900">Object</span> <span style="font-weight: bold"><span style="color: #000000">file: test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span>
+<span style="color: #009900">Exports</span><span style="color: #990000">:</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>
+<span style="color: #FF6600">ok</span>
+<span style="color: #993399">10</span><span style="color: #990000">></span> <span style="color: #FF6600">m</span>(<span style="color: #FF6600">second_module</span>)<span style="color: #990000">.</span>
+<span style="color: #009900">Module</span> <span style="color: #FF6600">second_module</span> <span style="color: #FF6600">compiled</span><span style="color: #990000">:</span> <span style="color: #009900">Date</span><span style="color: #990000">:</span> <span style="color: #009900">February</span> <span style="color: #993399">2</span> <span style="color: #993399">2013</span>, <span style="color: #009900">Time</span><span style="color: #990000">:</span> <span style="color: #993399">14.56</span>
+<span style="color: #009900">Compiler</span> <span style="color: #FF6600">options</span><span style="color: #990000">:</span> [<span style="color: #FF6600">from_core</span>]
+<span style="color: #009900">Object</span> <span style="font-weight: bold"><span style="color: #000000">file: test</span></span><span style="color: #990000">/</span><span style="font-weight: bold"><span style="color: #000000">mod_SUITE_data</span></span><span style="color: #990000">/</span><span style="color: #FF6600">two_modules</span><span style="color: #990000">.</span><span style="color: #FF6600">xerl</span>
+<span style="color: #009900">Exports</span><span style="color: #990000">:</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>
+ <span style="font-weight: bold"><span style="color: #000080">module_info</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>
+<span style="color: #FF6600">ok</span></tt></pre></div></div>
+<div class="paragraph"><p>So far so good!</p></div>
+<div class="paragraph"><p>What about the second snippet? It brings up many questions. What
+happens once a <code>mod</code> expression has been executed at
+compile time? If it’s an expression then it has to have a result,
+right? Right. We are still a bit lacking with expressions for now,
+though, so let’s get back to it after we add more.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.2/">View the source</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/xerl-0.3-atomic-expressions/index.html b/articles/xerl-0.3-atomic-expressions/index.html new file mode 100644 index 00000000..eca9f70f --- /dev/null +++ b/articles/xerl-0.3-atomic-expressions/index.html @@ -0,0 +1,306 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Xerl: atomic expressions</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link 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href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Xerl: atomic expressions</span></h1> + <p class="date"> + <span class="day">18</span> + <span class="month">Feb</span> + </p> +</header> + +<div class="paragraph"><p>We will be adding atomic integer expressions to our language.
+These look as follow in Erlang:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">42</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And the result of this expression is of course 42.</p></div>
+<div class="paragraph"><p>We will be running this expression at compile time, since we
+don’t have the means to run code at runtime yet. This will of
+course result in no module being compiled, but that’s OK, it will
+allow us to discuss a few important things we’ll have to plan for
+later on.</p></div>
+<div class="paragraph"><p>First, we must of course accept integers in the tokenizer.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>{<span style="color: #009900">D</span>}<span style="color: #990000">+</span> <span style="color: #990000">:</span> {<span style="color: #FF6600">token</span>, {<span style="font-weight: bold"><span style="color: #000080">integer</span></span>, <span style="color: #009900">TokenLine</span>, <span style="font-weight: bold"><span style="color: #000080">list_to_integer</span></span>(<span style="color: #009900">TokenChars</span>)}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>We must then accept atomic integer expressions in the parser.
+This is a simple change. The integer token is terminal so we need
+to add it to the list of terminals, and then we only need to add
+it as a possible expression.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">expr</span> <span style="color: #990000">-></span> <span style="color: #FF6600">integer</span> <span style="color: #990000">:</span> <span style="color: #FF6600">'$1'</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>A file containing only the number 42 (with no terminating dot)
+will give the following result when parsing it. This is incidentally
+the same result as when tokenizing.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>We must then evaluate it. We’re going to interpret it for now.
+Since the result of this expression is not stored in a variable,
+we are going to simply print it on the screen and discard it.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, [{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>, <span style="color: #990000">_</span>, <span style="color: #009900">Int</span>}|<span style="color: #009900">Tail</span>], <span style="color: #009900">Modules</span>) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">io:format</span></span>(<span style="color: #FF0000">"integer ~p~n"</span>, [<span style="color: #009900">Int</span>]),
+ <span style="font-weight: bold"><span style="color: #000000">execute</span></span>(<span style="color: #009900">Filename</span>, <span style="color: #009900">Tail</span>, <span style="color: #009900">Modules</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>You might think by now that what we’ve done so far this time
+is useless. It brings up many interesting questions though.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+What happens if a file contains two integers?
+</p>
+</li>
+<li>
+<p>
+Can we live without expression separators?
+</p>
+</li>
+<li>
+<p>
+Do we need an interpreter for the compile step?
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>This is what happens when we create a file that contains two
+integers on two separate lines:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>},{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">2</span>,<span style="color: #993399">43</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>And on the same lines:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>[{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">42</span>},{<span style="font-weight: bold"><span style="color: #000080">integer</span></span>,<span style="color: #993399">1</span>,<span style="color: #993399">43</span>}]</tt></pre></div></div>
+<div class="paragraph"><p>Does this mean we do not need separators between expressions?
+Not quite. The <code>+</code> and <code>-</code> operators are an
+example of why we can’t have nice things. They are ambiguous. They
+have two different meanings: make an atomic integer positive or
+negative, or perform an addition or a substraction between two
+integers. Without a separator you won’t be able to know if the
+following snippet is one or two expressions:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #993399">42</span> <span style="color: #990000">-</span> <span style="color: #993399">12</span></tt></pre></div></div>
+<div class="paragraph"><p>Can we use the line ending as an expression separator then?
+Some languages make whitespace important, often the line
+separator becomes the expression separator. I do not think this
+is the best idea, it can lead to errors. For example the following
+snippet would be two expressions:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Var</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">some_module:some_function</span></span>() <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000000">some_module:other_function</span></span>()
+ <span style="color: #990000">+</span> <span style="font-weight: bold"><span style="color: #000000">another_module:another_function</span></span>()</tt></pre></div></div>
+<div class="paragraph"><p>It is not obvious what would happen unless you are a veteran
+of the language, and so we will not go down that road. We will use
+an expression separator just like in Erlang: the comma. We will
+however allow a trailing comma to make copy pasting code easier,
+even if this means some old academics guy will go nuts about it
+later on. This trailing comma will be optional and simply discarded
+by the parser when encountered. We will implement this next.</p></div>
+<div class="paragraph"><p>The question as to how we will handle running expressions
+remains. We have two choices here: we can write an interpreter,
+or we can compile the code and run it. Writing an interpreter
+would require us to do twice the work, and we are lazy, so we will
+not do that.</p></div>
+<div class="paragraph"><p>You might already know that Erlang does not use the same code
+for compiling and for evaluating commands in the shell. The main
+reason for this is that in Erlang everything isn’t an expression.
+Indeed, the compiler compiles forms which contain expressions,
+but you can’t have forms in the shell.</p></div>
+<div class="paragraph"><p>How are we going to compile the code that isn’t part of a module
+then? What do we need to run at compile-time, anyway? The body of
+the file itself, of course. The body of module declarations. That’s
+about it.</p></div>
+<div class="paragraph"><p>For the file itself, we can simply compile it as a big function
+that will be executed. Then, everytime we encounter a module
+declaration, we will run the compiler on its body, making its body
+essentially a big function that will be executed. The same mechanism
+will be applied when we encounter a module declaration at runtime.</p></div>
+<div class="paragraph"><p>At runtime there’s nothing else for us to do, the result of this
+operation will load all the compiled modules. At compile time we
+will also want to save them to a file. We’ll see later how we can
+do that.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.3/">View the source</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/xerl-0.4-expression-separator/index.html b/articles/xerl-0.4-expression-separator/index.html new file mode 100644 index 00000000..a5be223f --- /dev/null +++ b/articles/xerl-0.4-expression-separator/index.html @@ -0,0 +1,211 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Xerl: expression separator</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Xerl: expression separator</span></h1> + <p class="date"> + <span class="day">01</span> + <span class="month">Mar</span> + </p> +</header> + +<div class="paragraph"><p>As promised we are adding an expression separator this time.
+This will be short and easy.</p></div>
+<div class="paragraph"><p>In the tokenizer we only need to add a line recognizing the
+comma as a valid token.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>, <span style="color: #990000">:</span> {<span style="color: #FF6600">token</span>, {<span style="color: #FF6600">','</span>, <span style="color: #009900">TokenLine</span>}}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Then we need to change the following lines in the parser:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$2'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And add a comma between the expressions on the second line:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
+<span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$3'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>That takes care of everything except the optional trailing
+comma at the end of our lists of expressions. We just need an
+additional rule to take care of this.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-></span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>That’s it.</p></div>
+<div class="paragraph"><p>Wondering why we don’t have this optional trailing comma in
+Erlang considering how easy it was and the number of people
+complaining about it? Yeah, me too. But that’s for someone else
+to answer.</p></div>
+<div class="paragraph"><p>Another change I want to talk about is a simple modification
+of the compiler code to use an <code>#env{}</code> record for
+tracking state instead of passing around individual variables.
+This will be required later on when we make modules into proper
+expressions so I thought it was a good idea to anticipate.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.4/">View the source</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + diff --git a/articles/xerl-0.5-intermediate-module/index.html b/articles/xerl-0.5-intermediate-module/index.html new file mode 100644 index 00000000..96e86e4f --- /dev/null +++ b/articles/xerl-0.5-intermediate-module/index.html @@ -0,0 +1,289 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Xerl: intermediate module</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Xerl: intermediate module</span></h1> + <p class="date"> + <span class="day">25</span> + <span class="month">Mar</span> + </p> +</header> + +<div class="paragraph"><p>Today we will start the work on the intermediate module
+that will be used to run the code for the expressions found
+in our file’s body, replacing our interpreter.</p></div>
+<div class="paragraph"><p>This is what we want to have when all the work is done:</p></div>
+<div class="listingblock">
+<div class="content">
+<pre><code>xerl -> tokens -> AST -> intermediate -> cerl</code></pre>
+</div></div>
+<div class="paragraph"><p>Today we will perform this work only on the atomic integer
+expression however, so we will not build any module at the end.
+We have a few more things to take care of before getting there.
+This does mean that we completely break compilation of modules
+though, so hopefully we can resolve that soon.</p></div>
+<div class="paragraph"><p>This intermediate representation is in the form of a module
+which contains a single function: <code>run/0</code>. This function
+contains all the expressions from our Xerl source file.</p></div>
+<div class="paragraph"><p>In the case of a Xerl source file only containing the integer
+<code>42</code>, we will obtain the following module ready to
+be executed:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000080">-module</span></span>(<span style="color: #FF6600">'$xerl_intermediate'</span>)<span style="color: #990000">.</span>
+<span style="font-weight: bold"><span style="color: #000080">-export</span></span>([<span style="font-weight: bold"><span style="color: #000000">run</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">run</span></span>() <span style="color: #990000">-></span>
+ <span style="color: #993399">42</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Running it will of course give us a result of <code>42</code>,
+the same we had when interpreting expressions.</p></div>
+<div class="paragraph"><p>The resulting Core Erlang code looks like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'$xerl_intermediate'</span> [<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-></span>
+ <span style="color: #993399">42</span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>The nice thing about doing it like this is that other than the
+definition of the intermediate module and its <code>run/0</code>
+function, we can use the same code we are using for generating
+the final Beam file. It may also be faster than interpreting
+if you have complex modules.</p></div>
+<div class="paragraph"><p>Of course this here only works for the simplest cases, as you
+cannot declare a module or a function inside another Erlang function.
+We will need to wrap these into function calls to the Xerl compiler
+that will take care of compiling them, making them available for
+any subsequent expression. We will also need to pass the environment
+to the <code>run</code> function to keep track of all this.</p></div>
+<div class="paragraph"><p>This does mean that we will have different code for compiling
+<code>fun</code> and <code>mod</code> expressions when creating
+the intermediate module. But the many other expressions don’t need
+any special care.</p></div>
+<div class="paragraph"><p>Right now we’ve used the <code>'$xerl_intermediate'</code> atom
+for the intermediate module name because we only have one, but we
+will need to have a more random name later on when we’ll implement
+modules this way.</p></div>
+<div class="paragraph"><p>The attentive mind will know by now that when compiling a Xerl
+file containing one module, we will need to compile two intermediate
+modules: one for the file body, and one for the module’s body. Worry
+not though, if we only detect <code>mod</code> instructions in the file
+body, we can just skip this phase.</p></div>
+<div class="paragraph"><p>While we’re at it, we’ll modify our code generator to handle lists
+of expressions, which didn’t actually work with integer literals
+before.</p></div>
+<div class="paragraph"><p>We’re going to use Core Erlang sequences for running the many
+expressions. Sequences work like <code>let</code>, except no value
+is actually bound. Perfect for our case, since we don’t support
+binding values at this time anyway.</p></div>
+<div class="paragraph"><p>Sequences have an argument and a body, both being Core Erlang
+expressions. The simplest way to have many expressions is to use
+a simple expression for the argument and a sequence for the rest
+of the expressions. When we encounter the last expression in the
+list, we do not create a sequence.</p></div>
+<div class="paragraph"><p>The result is this very simple function:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>([<span style="color: #009900">Expr</span>]) <span style="color: #990000">-></span>
+ <span style="font-weight: bold"><span style="color: #000000">expr</span></span>(<span style="color: #009900">Expr</span>);
+<span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>([<span style="color: #009900">Expr</span>|<span style="color: #009900">Exprs</span>]) <span style="color: #990000">-></span>
+ <span style="color: #009900">Arg</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">expr</span></span>(<span style="color: #009900">Expr</span>),
+ <span style="color: #009900">Body</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">comp_body</span></span>(<span style="color: #009900">Exprs</span>),
+ <span style="font-weight: bold"><span style="color: #000000">cerl:c_seq</span></span>(<span style="color: #009900">Arg</span>, <span style="color: #009900">Body</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>In the case of our example above, a sequence will not be created,
+we only have one expression. If we were to have <code>42, 43, 44</code>
+in our Xerl source file, we would have a result equivalent to the
+following before optimization:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000080">-module</span></span>(<span style="color: #FF6600">'$xerl_intermediate'</span>)<span style="color: #990000">.</span>
+<span style="font-weight: bold"><span style="color: #000080">-export</span></span>([<span style="font-weight: bold"><span style="color: #000000">run</span></span><span style="color: #990000">/</span><span style="color: #993399">0</span>])<span style="color: #990000">.</span>
+
+<span style="font-weight: bold"><span style="color: #000000">run</span></span>() <span style="color: #990000">-></span>
+ <span style="color: #993399">42</span>,
+ <span style="color: #993399">43</span>,
+ <span style="color: #993399">44</span><span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>And the result is of course <code>44</code>.</p></div>
+<div class="paragraph"><p>The resulting Core Erlang code looks like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #FF6600">module</span> <span style="color: #FF6600">'$xerl_intermediate'</span> [<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span>]
+ <span style="color: #FF6600">attributes</span> []
+<span style="color: #FF6600">'run'</span><span style="color: #990000">/</span><span style="color: #993399">0</span> <span style="color: #990000">=</span>
+ <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> () <span style="color: #990000">-></span>
+ <span style="color: #FF6600">do</span> <span style="color: #993399">42</span>
+ <span style="color: #FF6600">do</span> <span style="color: #993399">43</span>
+ <span style="color: #993399">44</span>
+<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
+<div class="paragraph"><p>Feels very lisp-y, right? Yep.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<a href="https://github.com/extend/xerl/blob/0.5/">View the source</a>
+</p>
+</li>
+</ul></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + |