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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>
<div class="sect1">
<h2 id="_name">Name</h2>
<div class="sectionbody">
<div class="paragraph"><p>cowboy_constraints:nonempty - Non-empty constraint</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">Description</h2>
<div class="sectionbody">
<div class="paragraph"><p>Constraint functions implement a number of different operations.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight
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">nonempty</span></span>(<span style="color: #FF6600">forward</span> | <span style="color: #FF6600">reverse</span>, <span style="color: #990000"><<>></span>) <span style="color: #990000">-></span> {<span style="color: #FF6600">error</span>, <span style="color: #FF6600">empty</span>}</tt></pre></div></div>
<div class="paragraph"><p>Reject empty values.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight
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">nonempty</span></span>(<span style="color: #FF6600">forward</span> | <span style="color: #FF6600">reverse</span>, <span style="color: #009900">Bin</span>) <span style="color: #990000">-></span> {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Bin</span>}
<span style="color: #009900">Bin</span> <span style="color: #990000">::</span> <span style="font-weight: bold"><span style="color: #000080">binary</span></span>()</tt></pre></div></div>
<div class="paragraph"><p>Accept any other binary values.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight
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">nonempty</span></span>(<span style="color: #FF6600">format_error</span>, <span style="color: #009900">Error</span>) <span style="color: #990000">-></span> <span style="color: #009900">HumanReadable</span>
<span style="color: #009900">Error</span> <span style="color: #990000">::</span> {<span style="color: #FF6600">empty</span>, <span style="color: #009900">Bin</span>}
<span style="color: #009900">HumanReadable</span> <span style="color: #990000">::</span> <span style="font-weight: bold"><span style="color: #000000">iolist</span></span>()</tt></pre></div></div>
<div class="paragraph"><p>Generate a human-readable error message.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_arguments">Arguments</h2>
<div class="sectionbody">
<div class="paragraph"><p>Arguments vary depending on the operation. Constraint
functions always take the operation type as first argument,
and the value as second argument.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_return_value">Return value</h2>
<div class="sectionbody">
<div class="paragraph"><p>The return value varies depending on the operation.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_changelog">Changelog</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
<strong>2.0</strong>: Interface modified to allow for a variety of operations.
</p>
</li>
<li>
<p>
<strong>1.0</strong>: Constraint introduced.
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_examples">Examples</h2>
<div class="sectionbody">
<div class="paragraph"><p>This function is not meant to be called directly.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">See also</h2>
<div class="sectionbody">
<div class="paragraph"><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></div>
</div>
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<h3>
Cowboy
2.0
Function Reference
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
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