<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
    "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">

<head>
	<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
	<title>Logtalk built-in predicate: extends_protocol/2-3</title>
	<link rel="stylesheet" href="../../screen.css" type="text/css" media="screen"/>
	<link rel="stylesheet" href="../../print.css" type="text/css" media="print"/>
</head>

<body>

<div class="top-left">Logtalk reference manual</div> 
<div class="top-right">Built-in predicate: extends_protocol/2-3</div>
<div class="bottom-left"><span class="page"/></div> 
<div class="bottom-right"><span class="page"/></div>
<div class="navtop"><a href="../../index.html">contents</a> &gt; <a href="../index.html">reference manual</a> &gt; <a href="../index.html#builtins">built-in predicates</a></div>

<h2 class="code">extends_protocol/2-3</h2>


<h4>Description</h4>

<pre>extends_protocol(Protocol1, Protocol2)

extends_protocol(Protocol1, Protocol2, Scope)</pre>
<p>
Enumerates, by backtracking, all pairs of protocols such that the first one extends the second. 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>extends_protocol(?protocol_identifier, ?protocol_identifier)

extends_protocol(?protocol_identifier, ?protocol_identifier, ?scope)</pre>

<h4>Errors</h4>

<dl class="errors">
	<dt>Protocol1 is neither a variable nor a valid protocol identifier:</dt>
		<dd><code>type_error(protocol_identifier, Protocol1)</code></dd>
	<dt>Protocol2 is neither a variable nor a valid protocol identifier:</dt>
		<dd><code>type_error(protocol_identifier, Protocol2)</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>| ?- extends_protocol(listp, Protocol).

| ?- extends_protocol(Protocol, termp, private).</pre>

<div class="footer">
	<div class="navbottom"><a href="extends_object2_3.html">previous</a> | <a href="../../glossary.html">glossary</a> | <a href="implements_protocol2_3.html">next</a></div>
	<div class="copyright">Copyright &copy; <a href="mailto:pmoura@logtalk.org">Paulo Moura</a> &mdash; <a href="http://www.logtalk.org">Logtalk.org</a></div>
	<div class="footnote">
		<span class="validators"><a href="http://validator.w3.org/check/referer">XHTML</a> + <a href="http://jigsaw.w3.org/css-validator/check/referer">CSS</a></span>
		<span class="date">Last updated on: November 16, 2005</span>
	</div>
</div>

</body>
</html>