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<title>Nine Nines: cowboy_constraints:nonempty(3)</title>
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<h1 class="lined-header"><span>cowboy_constraints:nonempty(3)</span></h1>
<h2 id="_name">Name</h2>
<p>cowboy_constraints:nonempty - Non-empty constraint</p>
<h2 id="_description">Description</h2>
<p>Constraint functions implement a number of different operations.</p>
<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><b><font color="#000000">nonempty</font></b>(<font color="#FF6600">forward</font> | <font color="#FF6600">reverse</font>, <font color="#990000"><<>></font>) <font color="#990000">-></font> {<font color="#FF6600">error</font>, <font color="#FF6600">empty</font>}</tt></pre>
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<p>Reject empty values.</p>
<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><b><font color="#000000">nonempty</font></b>(<font color="#FF6600">forward</font> | <font color="#FF6600">reverse</font>, <font color="#009900">Bin</font>) <font color="#990000">-></font> {<font color="#FF6600">ok</font>, <font color="#009900">Bin</font>}
<font color="#009900">Bin</font> <font color="#990000">::</font> <b><font color="#000080">binary</font></b>()</tt></pre>
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<p>Accept any other binary values.</p>
<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><b><font color="#000000">nonempty</font></b>(<font color="#FF6600">format_error</font>, <font color="#009900">Error</font>) <font color="#990000">-></font> <font color="#009900">HumanReadable</font>
<font color="#009900">Error</font> <font color="#990000">::</font> {<font color="#FF6600">empty</font>, <font color="#009900">Bin</font>}
<font color="#009900">HumanReadable</font> <font color="#990000">::</font> <b><font color="#000000">iolist</font></b>()</tt></pre>
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<p>Generate a human-readable error message.</p>
<h2 id="_arguments">Arguments</h2>
<p>Arguments vary depending on the operation. Constraint functions always take the operation type as first argument, and the value as second argument.</p>
<h2 id="_return_value">Return value</h2>
<p>The return value varies depending on the operation.</p>
<h2 id="_changelog">Changelog</h2>
<ul><li><strong>2.0</strong>: Interface modified to allow for a variety of operations.
</li>
<li><strong>1.0</strong>: Constraint introduced.
</li>
</ul>
<h2 id="_examples">Examples</h2>
<p>This function is not meant to be called directly.</p>
<h2 id="_see_also">See also</h2>
<p><a href="../cowboy_constraints">cowboy_constraints(3)</a>, <a href="../cowboy_constraints.int">cowboy_constraints:int(3)</a>, <a href="../cowboy_router">cowboy_router(3)</a>, <a href="../cowboy_req.match_cookies">cowboy_req:match_cookies(3)</a>, <a href="../cowboy_req.match_qs">cowboy_req:match_qs(3)</a></p>
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