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<h1>
<small class="visible-xs">Elixir v1.7.2</small>
Function
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/function.ex#L1" title="View Source" class="view-source" rel="help">
<span class="icon-code" aria-hidden="true"></span>
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</h1>
<section id="moduledoc">
<p>A set of functions for working with functions.</p>
<p>There are two types of captured functions: <strong>external</strong> and <strong>local</strong>.
External functions are functions residing in modules that are captured
with <a href="Kernel.SpecialForms.html#&amp;/1"><code class="inline">&/1</code></a>, such as <code class="inline">&String.length/1</code>. Local functions are anonymous functions
defined with <a href="Kernel.SpecialForms.html#fn/1"><code class="inline">fn/1</code></a> or with the capture operator <a href="Kernel.SpecialForms.html#&amp;/1"><code class="inline">&/1</code></a> using <code class="inline">&1</code>, <code class="inline">&2</code>,
and so on as replacements.</p>
</section>
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Summary
</h1>
<div class="summary-types summary">
<h2>
<a href="#types">Types</a>
</h2>
<div class="summary-row">
<div class="summary-signature">
<a href="#t:information/0">information()</a>
</div>
</div>
</div>
<div class="summary-functions summary">
<h2>
<a href="#functions">Functions</a>
</h2>
<div class="summary-row">
<div class="summary-signature">
<a href="#capture/3">capture(module, function_name, arity)</a>
</div>
<div class="summary-synopsis"><p>Captures the given function</p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#info/1">info(fun)</a>
</div>
<div class="summary-synopsis"><p>Returns a keyword list with information about a function</p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#info/2">info(fun, item)</a>
</div>
<div class="summary-synopsis"><p>Returns a specific information about the function</p>
</div>
</div>
</div>
</section>
<section id="types" class="details-list">
<h1 class="section-heading">
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Types
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<span class="signature">information()</span>
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/function.ex#L12" class="view-source" rel="help" title="View Source">
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<div class="specs">
<pre>information() ::
:arity
| :env
| :index
| :module
| :name
| :new_index
| :new_uniq
| :pid
| :type
| :uniq</pre>
</div>
</div>
<section class="docstring">
</section>
</div>
</div>
</section>
<section id="functions" class="details-list">
<h1 class="section-heading">
<a class="hover-link" href="#functions">
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Functions
</h1>
<div class="detail" id="capture/3">
<div class="detail-header">
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<span class="signature">capture(module, function_name, arity)</span>
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/function.ex#L37" class="view-source" rel="help" title="View Source">
<span class="icon-code" aria-hidden="true"></span>
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</a>
<span class="note">(since 1.7.0)</span>
<div class="specs">
<pre>capture(<a href="typespecs.html#built-in-types">module</a>(), <a href="typespecs.html#basic-types">atom</a>(), <a href="typespecs.html#built-in-types">arity</a>()) :: (... -> <a href="typespecs.html#basic-types">any</a>())</pre>
</div>
</div>
<section class="docstring">
<p>Captures the given function.</p>
<p>Inlined by the compiler.</p>
<h2 id="capture/3-examples" class="section-heading">
<a href="#capture/3-examples" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a>
Examples
</h2>
<pre><code class="nohighlight makeup elixir"><span class="gp unselectable">iex> </span><span class="nc">Function</span><span class="o">.</span><span class="n">capture</span><span class="p" data-group-id="9682076812-1">(</span><span class="nc">String</span><span class="p">,</span><span class="w"> </span><span class="ss">:length</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="9682076812-1">)</span><span class="w">
</span><span class="o">&</span><span class="nc">String</span><span class="o">.</span><span class="n">length</span><span class="o">/</span><span class="mi">1</span></code></pre>
</section>
</div>
<div class="detail" id="info/1">
<div class="detail-header">
<a href="#info/1" class="detail-link" title="Link to this function">
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</a>
<span class="signature">info(fun)</span>
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/function.ex#L98" class="view-source" rel="help" title="View Source">
<span class="icon-code" aria-hidden="true"></span>
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</a>
<span class="note">(since 1.7.0)</span>
<div class="specs">
<pre>info((... -> <a href="typespecs.html#basic-types">any</a>())) :: [{<a href="#t:information/0">information</a>(), <a href="typespecs.html#built-in-types">term</a>()}]</pre>
</div>
</div>
<section class="docstring">
<p>Returns a keyword list with information about a function.</p>
<p>The returned keys (with the corresponding possible values) for
all types of functions (local and external) are the following:</p>
<ul>
<li><p><code class="inline">:type</code> - <code class="inline">:local</code> (for anonymous functions) or <code class="inline">:external</code> (for
named functions).</p>
</li>
<li><p><code class="inline">:module</code> - an atom which is the module where the function is defined when
anonymous or the module which the function refers to when it’s a named function.</p>
</li>
<li><p><code class="inline">:arity</code> - (integer) the number of arguments the function is to be called with.</p>
</li>
<li><p><code class="inline">:name</code> - (atom) the name of the function.</p>
</li>
<li><p><code class="inline">:env</code> - a list of the environment or free variables. For named
functions, the returned list is always empty.</p>
</li>
</ul>
<p>When <code class="inline">fun</code> is an anonymous function (that is, the type is <code class="inline">:local</code>), the following
additional keys are returned:</p>
<ul>
<li><p><code class="inline">:pid</code> - PID of the process that originally created the function.</p>
</li>
<li><p><code class="inline">:index</code> - (integer) an index into the module function table.</p>
</li>
<li><p><code class="inline">:new_index</code> - (integer) an index into the module function table.</p>
</li>
<li><p><code class="inline">:new_uniq</code> - (binary) a unique value for this function. It’s
calculated from the compiled code for the entire module.</p>
</li>
<li><p><code class="inline">:uniq</code> - (integer) a unique value for this function. This integer is
calculated from the compiled code for the entire module.</p>
</li>
</ul>
<p><strong>Note</strong>: this function must be used only for debugging purposes.</p>
<p>Inlined by the compiler.</p>
<h2 id="info/1-examples" class="section-heading">
<a href="#info/1-examples" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a>
Examples
</h2>
<pre><code class="nohighlight makeup elixir"><span class="gp unselectable">iex> </span><span class="n">fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k" data-group-id="1667166345-1">fn</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">-></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="k" data-group-id="1667166345-1">end</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="n">info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="1667166345-2">(</span><span class="n">fun</span><span class="p" data-group-id="1667166345-2">)</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Keyword</span><span class="o">.</span><span class="n">get</span><span class="p" data-group-id="1667166345-3">(</span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="ss">:arity</span><span class="p" data-group-id="1667166345-3">)</span><span class="w">
</span><span class="mi">1</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Keyword</span><span class="o">.</span><span class="n">get</span><span class="p" data-group-id="1667166345-4">(</span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="ss">:type</span><span class="p" data-group-id="1667166345-4">)</span><span class="w">
</span><span class="ss">:local</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="n">fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="nc">String</span><span class="o">.</span><span class="n">length</span><span class="o">/</span><span class="mi">1</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="n">info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="1667166345-5">(</span><span class="n">fun</span><span class="p" data-group-id="1667166345-5">)</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Keyword</span><span class="o">.</span><span class="n">get</span><span class="p" data-group-id="1667166345-6">(</span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="ss">:type</span><span class="p" data-group-id="1667166345-6">)</span><span class="w">
</span><span class="ss">:external</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Keyword</span><span class="o">.</span><span class="n">get</span><span class="p" data-group-id="1667166345-7">(</span><span class="n">info</span><span class="p">,</span><span class="w"> </span><span class="ss">:name</span><span class="p" data-group-id="1667166345-7">)</span><span class="w">
</span><span class="ss">:length</span></code></pre>
</section>
</div>
<div class="detail" id="info/2">
<div class="detail-header">
<a href="#info/2" class="detail-link" title="Link to this function">
<span class="icon-link" aria-hidden="true"></span>
<span class="sr-only">Link to this function</span>
</a>
<span class="signature">info(fun, item)</span>
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/function.ex#L136" class="view-source" rel="help" title="View Source">
<span class="icon-code" aria-hidden="true"></span>
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</a>
<span class="note">(since 1.7.0)</span>
<div class="specs">
<pre>info((... -> <a href="typespecs.html#basic-types">any</a>()), item) :: {item, <a href="typespecs.html#built-in-types">term</a>()} when item: <a href="#t:information/0">information</a>()</pre>
</div>
</div>
<section class="docstring">
<p>Returns a specific information about the function.</p>
<p>The returned information is a two-element tuple in the shape of
<code class="inline">{info, value}</code>.</p>
<p>For any function, the information asked for can be any of the atoms
<code class="inline">:module</code>, <code class="inline">:name</code>, <code class="inline">:arity</code>, <code class="inline">:env</code>, or <code class="inline">:type</code>.</p>
<p>For anonymous functions, there is also information about any of the
atoms <code class="inline">:index</code>, <code class="inline">:new_index</code>, <code class="inline">:new_uniq</code>, <code class="inline">:uniq</code>, and <code class="inline">:pid</code>.
For a named function, the value of any of these items is always the
atom <code class="inline">:undefined</code>.</p>
<p>For more information on each of the possible returned values, see
<a href="#info/1"><code class="inline">info/1</code></a>.</p>
<p>Inlined by the compiler.</p>
<h2 id="info/2-examples" class="section-heading">
<a href="#info/2-examples" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a>
Examples
</h2>
<pre><code class="nohighlight makeup elixir"><span class="gp unselectable">iex> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k" data-group-id="6816937796-1">fn</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">-></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="k" data-group-id="6816937796-1">end</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="6816937796-2">(</span><span class="n">f</span><span class="p">,</span><span class="w"> </span><span class="ss">:arity</span><span class="p" data-group-id="6816937796-2">)</span><span class="w">
</span><span class="p" data-group-id="6816937796-3">{</span><span class="ss">:arity</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p" data-group-id="6816937796-3">}</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="6816937796-4">(</span><span class="n">f</span><span class="p">,</span><span class="w"> </span><span class="ss">:type</span><span class="p" data-group-id="6816937796-4">)</span><span class="w">
</span><span class="p" data-group-id="6816937796-5">{</span><span class="ss">:type</span><span class="p">,</span><span class="w"> </span><span class="ss">:local</span><span class="p" data-group-id="6816937796-5">}</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="n">fun</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="nc">String</span><span class="o">.</span><span class="n">length</span><span class="o">/</span><span class="mi">1</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="6816937796-6">(</span><span class="n">fun</span><span class="p">,</span><span class="w"> </span><span class="ss">:name</span><span class="p" data-group-id="6816937796-6">)</span><span class="w">
</span><span class="p" data-group-id="6816937796-7">{</span><span class="ss">:name</span><span class="p">,</span><span class="w"> </span><span class="ss">:length</span><span class="p" data-group-id="6816937796-7">}</span><span class="w">
</span><span class="gp unselectable">iex> </span><span class="nc">Function</span><span class="o">.</span><span class="n">info</span><span class="p" data-group-id="6816937796-8">(</span><span class="n">fun</span><span class="p">,</span><span class="w"> </span><span class="ss">:pid</span><span class="p" data-group-id="6816937796-8">)</span><span class="w">
</span><span class="p" data-group-id="6816937796-9">{</span><span class="ss">:pid</span><span class="p">,</span><span class="w"> </span><span class="ss">:undefined</span><span class="p" data-group-id="6816937796-9">}</span></code></pre>
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