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author | Loïc Hoguin <[email protected]> | 2017-10-03 13:39:41 +0200 |
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committer | Loïc Hoguin <[email protected]> | 2017-10-03 13:39:41 +0200 |
commit | b5d4cb91f80c833795a2d87050c3674bb7aecdc5 (patch) | |
tree | 62bf0ad8326006fcd3407fcb7c34c844c0dc0874 /articles/xerl-0.2-two-modules/index.html | |
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diff --git a/articles/xerl-0.2-two-modules/index.html b/articles/xerl-0.2-two-modules/index.html index 632248a0..279aaa23 100644 --- a/articles/xerl-0.2-two-modules/index.html +++ b/articles/xerl-0.2-two-modules/index.html @@ -7,7 +7,7 @@ <meta name="description" content=""> <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> - <meta name="generator" content="Hugo 0.17" /> + <meta name="generator" content="Hugo 0.26" /> <title>Nine Nines: Xerl: two modules</title> @@ -74,149 +74,149 @@ </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>
+<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> @@ -225,55 +225,107 @@ though, so let’s get back to it after we add more.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> - <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-rc.2/">Cowboy 2.0 release candidate 2</a></li> + + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-rc.2/">Cowboy 2.0 release candidate 2</a></li> + + + + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-rc.1/">Cowboy 2.0 release candidate 1</a></li> + - <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-rc.1/">Cowboy 2.0 release candidate 1</a></li> + + <li><a href="https://ninenines.eu/articles/the-elephant-in-the-room/">The elephant in the room</a></li> + - <li><a href="https://ninenines.eu/articles/the-elephant-in-the-room/">The elephant in the room</a></li> + + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + - 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