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80 lines
3.2 KiB
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80 lines
3.2 KiB
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<title>Logtalk built-in method: clause/2</title>
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<div class="top-left">Logtalk reference manual</div>
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<div class="top-right">Built-in method: clause/2</div>
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<div class="bottom-left"><span class="page"/></div>
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<div class="bottom-right"><span class="page"/></div>
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<div class="navtop"><a href="../../index.html">contents</a> > <a href="../index.html">reference manual</a> > <a href="../index.html#methods">built-in methods</a></div>
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<h2 class="codenp">clause/2<span id="methods_clause2"/></h2>
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<h4>Description</h4>
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<pre>clause(Head, Body)</pre>
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<p>
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Enumerates, by backtracking, the clauses of an object's dynamic predicates.
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</p>
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<h4>Template and modes</h4>
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<pre>clause(+callable, ?body)</pre>
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<h4>Errors</h4>
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<dl>
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<dt>Head is a variable:</dt>
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<dd><code>instantiation_error</code></dd>
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<dt>Head is a neither a variable nor a callable term:</dt>
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<dd><code>type_error(callable, Head)</code></dd>
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<dt>Body is a neither a variable nor a callable term:</dt>
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<dd><code>type_error(callable, Body)</code></dd>
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<dt>The predicate indicator of Head is that of a private predicate:</dt>
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<dd><code>permission_error(access, private_predicate, Head)</code></dd>
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<dt>The predicate indicator of Head is that of a protected predicate:</dt>
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<dd><code>permission_error(access, protected_predicate, Head)</code></dd>
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<dt>The predicate indicator of Head is that of a static predicate:</dt>
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<dd><code>permission_error(access, static_predicate, Head)</code></dd>
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<dt>Head is not a declared predicate:</dt>
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<dd><code>existence_error(predicate_declaration, Head)</code></dd>
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</dl>
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<h4>Examples</h4>
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<dl>
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<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>
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<dd><code>clause(Head, Body)</code></dd>
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<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>
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<dd><code>::clause(Head, Body)</code></dd>
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<dt>To retrieve a matching clause of a public dynamic predicate in an object:</dt>
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<dd><code>Object::clause(Head, Body)</code></dd>
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</dl>
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<div class="footer">
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<div class="copyright">
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<span>Copyright © <a href="mailto:pmoura@logtalk.org">Paulo Moura</a> — <a href="http://logtalk.org">Logtalk.org</a></span><br/>
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<span>Last updated on: October 26, 2006</span>
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