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<div class="top-left">Logtalk reference manual</div> 
<div class="top-right">Built-in predicate: implements_protocol/2-3</div>
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<h2 class="code">implements_protocol/2-3</h2>


<h4>Description</h4>

<pre>implements_protocol(Object, Protocol)
implements_protocol(Category, Protocol)

implements_protocol(Object, Protocol, Scope)
implements_protocol(Category, Protocol, Scope)</pre>
<p>
Enumerates, by backtracking, all pairs of entities such that an object or a category implements a protocol. The relation scope is represented by the atoms <code>public</code>, <code>protected</code>, and <code>private</code>.
</p>

<h4>Template and modes</h4>

<pre>implements_protocol(?object_identifier, ?protocol_identifier)
implements_protocol(?category_identifier, ?protocol_identifier)

implements_protocol(?object_identifier, ?protocol_identifier, ?scope)
implements_protocol(?category_identifier, ?protocol_identifier, ?scope)</pre>

<h4>Errors</h4>

<dl class="errors">
	<dt>Object is neither a variable nor a valid object identifier:</dt>
		<dd><code>type_error(object_identifier, Object)</code></dd>
	<dt>Category is neither a variable nor a valid category identifier:</dt>
		<dd><code>type_error(category_identifier, Category)</code></dd>
	<dt>Protocol is neither a variable nor a valid protocol identifier:</dt>
		<dd><code>type_error(protocol_identifier, Protocol)</code></dd>
	<dt>Scope is neither a variable nor a valid entity scope:</dt>
		<dd><code>type_error(scope, Scope)</code></dd>
</dl>

<h4>Examples</h4>

<pre>| ?- implements_protocol(List, listp).

| ?- implements_protocol(List, listp, public).</pre>

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