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<h1>
<small class="visible-xs">Elixir v1.7.2</small>
Inspect <small>protocol</small>
<a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/elixir/lib/inspect.ex#L6" title="View Source" class="view-source" rel="help">
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<p>The <a href="Inspect.html#content"><code class="inline">Inspect</code></a> protocol converts an Elixir data structure into an
algebra document.</p>
<p>This documentation refers to implementing the <a href="Inspect.html#content"><code class="inline">Inspect</code></a> protocol
for your own data structures. To learn more about using inspect,
see <a href="Kernel.html#inspect/2"><code class="inline">Kernel.inspect/2</code></a> and <a href="IO.html#inspect/2"><code class="inline">IO.inspect/2</code></a>.</p>
<p>The <a href="#inspect/2"><code class="inline">inspect/2</code></a> function receives the entity to be inspected
followed by the inspecting options, represented by the struct
<a href="Inspect.Opts.html"><code class="inline">Inspect.Opts</code></a>. Building of the algebra document is done with
<a href="Inspect.Algebra.html"><code class="inline">Inspect.Algebra</code></a>.</p>
<h2 id="module-examples" class="section-heading">
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Examples
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<p>Many times, inspecting a structure can be implemented in function
of existing entities. For example, here is <a href="MapSet.html"><code class="inline">MapSet</code></a>’s <code class="inline">inspect</code>
implementation:</p>
<pre><code class="nohighlight makeup elixir"><span class="kd">defimpl</span><span class="w"> </span><span class="nc">Inspect</span><span class="p">,</span><span class="w"> </span><span class="ss">for</span><span class="p">:</span><span class="w"> </span><span class="nc">MapSet</span><span class="w"> </span><span class="k" data-group-id="1746723684-1">do</span><span class="w">
</span><span class="kn">import</span><span class="w"> </span><span class="nc">Inspect.Algebra</span><span class="w">
</span><span class="kd">def</span><span class="w"> </span><span class="nf">inspect</span><span class="p" data-group-id="1746723684-2">(</span><span class="n">dict</span><span class="p">,</span><span class="w"> </span><span class="n">opts</span><span class="p" data-group-id="1746723684-2">)</span><span class="w"> </span><span class="k" data-group-id="1746723684-3">do</span><span class="w">
</span><span class="n">concat</span><span class="p" data-group-id="1746723684-4">(</span><span class="p" data-group-id="1746723684-5">[</span><span class="s">"#MapSet<"</span><span class="p">,</span><span class="w"> </span><span class="n">to_doc</span><span class="p" data-group-id="1746723684-6">(</span><span class="nc">MapSet</span><span class="o">.</span><span class="n">to_list</span><span class="p" data-group-id="1746723684-7">(</span><span class="n">dict</span><span class="p" data-group-id="1746723684-7">)</span><span class="p">,</span><span class="w"> </span><span class="n">opts</span><span class="p" data-group-id="1746723684-6">)</span><span class="p">,</span><span class="w"> </span><span class="s">">"</span><span class="p" data-group-id="1746723684-5">]</span><span class="p" data-group-id="1746723684-4">)</span><span class="w">
</span><span class="k" data-group-id="1746723684-3">end</span><span class="w">
</span><span class="k" data-group-id="1746723684-1">end</span></code></pre>
<p>The <code class="inline">concat/1</code> function comes from <a href="Inspect.Algebra.html"><code class="inline">Inspect.Algebra</code></a> and it
concatenates algebra documents together. In the example above,
it is concatenating the string <code class="inline">"MapSet<"</code> (all strings are
valid algebra documents that keep their formatting when pretty
printed), the document returned by <a href="Inspect.Algebra.html#to_doc/2"><code class="inline">Inspect.Algebra.to_doc/2</code></a> and the
other string <code class="inline">">"</code>.</p>
<p>Since regular strings are valid entities in an algebra document,
an implementation of inspect may simply return a string,
although that will devoid it of any pretty-printing.</p>
<h2 id="module-error-handling" class="section-heading">
<a href="#module-error-handling" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a>
Error handling
</h2>
<p>In case there is an error while your structure is being inspected,
Elixir will raise an <a href="ArgumentError.html"><code class="inline">ArgumentError</code></a> error and will automatically fall back
to a raw representation for printing the structure.</p>
<p>You can however access the underlying error by invoking the Inspect
implementation directly. For example, to test Inspect.MapSet above,
you can invoke it as:</p>
<pre><code class="nohighlight makeup elixir"><span class="nc">Inspect.MapSet</span><span class="o">.</span><span class="n">inspect</span><span class="p" data-group-id="3015875645-1">(</span><span class="nc">MapSet</span><span class="o">.</span><span class="n">new</span><span class="p" data-group-id="3015875645-2">(</span><span class="p" data-group-id="3015875645-2">)</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="3015875645-3">%</span><span class="nc" data-group-id="3015875645-3">Inspect.Opts</span><span class="p" data-group-id="3015875645-3">{</span><span class="p" data-group-id="3015875645-3">}</span><span class="p" data-group-id="3015875645-1">)</span></code></pre>
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<a href="#inspect/2">inspect(term, opts)</a>
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