<?xml version="1.0" encoding="utf-8"?> <!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="application/xml+xhtml; charset=utf-8" /> <title>Logtalk built-in method: retract/1</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 method: retract/1</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> > <a href="../index.html">reference manual</a> > <a href="../index.html#methods">built-in methods</a></div> <h2 id="methods_retract1" class="codenp">retract/1</h2> <h4>Description</h4> <pre>retract(Clause) retract((Head:-Body))</pre> <p> Retracts a dynamic clause from an object. </p> <h4>Template and modes</h4> <pre>retract(+clause)</pre> <h4>Errors</h4> <dl> <dt>Head is a variable:</dt> <dd><code>instantiation_error</code></dd> <dt>Head is neither a variable nor a callable term:</dt> <dd><code>type_error(callable, Head)</code></dd> <dt>The predicate indicator of Head is that of a private predicate:</dt> <dd><code>permission_error(modify, private_predicate, Head)</code></dd> <dt>The predicate indicator of Head is that of a protected predicate:</dt> <dd><code>permission_error(modify, protected_predicate, Head)</code></dd> <dt>The predicate indicator of Head is that of a static predicate:</dt> <dd><code>permission_error(modify, static_predicate, Head)</code></dd> <dt>The predicate indicator of Head is not declared:</dt> <dd><code>existence_error(predicate_declaration, Head)</code></dd> </dl> <h4>Examples</h4> <dl> <dt>To retract 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>retract(Clause)</code></dd> <dt>To retract 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>::retract(Clause)</code></dd> <dt>To retract a matching clause of a public dynamic predicate in an object:</dt> <dd><code>Object::retract(Clause)</code></dd> </dl> <div class="footer"> <div class="copyright"> <span>Copyright © <a href="mailto:pmoura@logtalk.org">Paulo Moura</a> — <a href="http://logtalk.org">Logtalk.org</a></span><br/> <span>Last updated on: October 26, 2006</span> </div> <div class="navbottom"> <span><a href="clause2.html">previous</a> | <a href="../../glossary.html">glossary</a> | <a href="retractall1.html">next</a></span><br/> <span><a href="http://validator.w3.org/check/referer">XHTML</a> + <a href="http://jigsaw.w3.org/css-validator/check/referer">CSS</a></span> </div> </div> </body> </html>