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<title>Logtalk built-in method: clause/2</title>
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<div class="top-left">Logtalk reference manual</div>
<div class="top-right">Built-in method: clause/2</div>
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<h2 class="codenp">clause/2<span id="methods_clause2"/></h2>
<h4>Description</h4>
<pre>clause(Head, Body)</pre>
<p>
Enumerates, by backtracking, the clauses of an object's dynamic predicates.
</p>
<h4>Template and modes</h4>
<pre>clause(+callable, ?body)</pre>
<h4>Errors</h4>
<dl>
<dt>Head is a variable:</dt>
<dd><code>instantiation_error</code></dd>
<dt>Head is a neither a variable nor a callable term:</dt>
<dd><code>type_error(callable, Head)</code></dd>
<dt>Body is a neither a variable nor a callable term:</dt>
<dd><code>type_error(callable, Body)</code></dd>
<dt>The predicate indicator of Head is that of a private predicate:</dt>
<dd><code>permission_error(access, private_predicate, Head)</code></dd>
<dt>The predicate indicator of Head is that of a protected predicate:</dt>
<dd><code>permission_error(access, protected_predicate, Head)</code></dd>
<dt>The predicate indicator of Head is that of a static predicate:</dt>
<dd><code>permission_error(access, static_predicate, Head)</code></dd>
<dt>Head is not a declared predicate:</dt>
<dd><code>existence_error(predicate_declaration, Head)</code></dd>
</dl>
<h4>Examples</h4>
<dl>
<dt>To retrieve a matching clause of any dynamic predicate in <a class="glossary" title="Go to glossary definition" href="../../glossary.html#this">this</a>:</dt>
<dd><code>clause(Head, Body)</code></dd>
<dt>To retrieve a matching clause of a public or protected dynamic predicate in <a class="glossary" title="Go to glossary definition" href="../../glossary.html#self">self</a>:</dt>
<dd><code>::clause(Head, Body)</code></dd>
<dt>To retrieve a matching clause of a public dynamic predicate in an object:</dt>
<dd><code>Object::clause(Head, Body)</code></dd>
</dl>
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<span>Last updated on: October 26, 2006</span>
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