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82 lines
2.6 KiB
HTML
82 lines
2.6 KiB
HTML
<!doctype html public "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>clause/2</title>
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<link rel=stylesheet href="../../styles.css" type="text/css">
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</head>
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<body>
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<h2><code><a class="back" title="Return to index" href="../index.html#clause2">clause/2</a></code></h2>
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<hr />
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<h4>Description</h4>
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<blockquote>
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<pre>
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clause(Head, Body)
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</pre>
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<p>
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Enumerates, by backtracking, the clauses of an object's dynamic predicates. Note however that if the clauses for the dynamic predicate are contained in a category the predicate will fail.
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</p>
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</blockquote>
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<h4>Template and modes</h4>
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<blockquote>
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<pre>
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clause(?callable, ?body)
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</pre>
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</blockquote>
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<h3>Errors</h3>
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<blockquote>
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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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</blockquote>
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<h4>Examples</h4>
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<blockquote>
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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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</blockquote>
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<hr />
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<p class="center">
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<strong><a href="assertz1.html">Previous</a> | <a href="retract1.html">Next</a> | <a href="../index.html">Table of Contents</a> | <a href="../../bibliography.html">Bibliography</a> | <a href="../../glossary.html">Glossary</a></strong>
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</p>
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<p class="center">
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Last updated on: July 4, 2000
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</p>
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<hr />
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</body>
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</html>
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