This repository has been archived on 2023-08-20. You can view files and clone it, but cannot push or open issues or pull requests.
yap-6.3/Logtalk/manuals/refman/methods/parameter2.html
pmoura 80c28e1507 Logtalk 2.25.1 files.
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1357 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
2005-08-08 12:13:45 +00:00

84 lines
2.8 KiB
HTML

<?xml version="1.0" encoding="iso-8859-1"?>
<?xml-stylesheet type="text/css" href="../../styles.css" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>Logtalk built-in method: parameter/2</title>
<link rel="stylesheet" href="../../styles.css" type="text/css" />
</head>
<body>
<div class="navtop">
<a href="../../index.html">contents</a> &gt; <a href="../index.html">reference manual</a> &gt; <a href="../index.html#methods">built-in methods</a>
</div>
<h2><code>parameter/2</code></h2>
<h4>Description</h4>
<blockquote>
<pre>parameter(Number, Term)</pre>
<p>
Normally used only in <a class="glossary" title="Go to glossary definition" href="../../glossary.html#parametric">parametric objects</a>, this method returns parameter values by using the parameter position in the object identifier. Note that this predicate implies an instantiation between its second argument and the corresponding implicit context argument in the predicate containing the call. This instantiation occurs at the clause head, not at the clause body. See also <a href="this1.html"><code>this/1</code></a>.
</p>
</blockquote>
<h4>Template and modes</h4>
<blockquote>
<pre>parameter(+integer, ?term)</pre>
</blockquote>
<h4>Errors</h4>
<blockquote>
<dl>
<dt>Number is a variable:</dt>
<dd><code>instantiation_error</code></dd>
<dt>Number is neither a variable nor an integer value:</dt>
<dd><code>type_error(integer, Number)</code></dd>
<dt>Object identifier is not a compound term:</dt>
<dd><code>type_error(compound, Object)</code></dd>
<dt>Number is a negative integer value:</dt>
<dd><code>domain_error(not_less_than_zero, Number)</code></dd>
</dl>
</blockquote>
<h4>Examples</h4>
<blockquote>
<pre>:- object(box(_colour, _weight)).
...
colour(Colour) :- % this clause is translated to a fact upon compilation
parameter(1, Colour).
heavy :-
parameter(2, Weight), % after compilation, the >/2 call will be the first
Weight > 10. % condition on the clause body
...</pre>
</blockquote>
<div class="navbottom">
<a href="../index.html#methods">previous</a> | <a href="../../glossary.html">glossary</a> | <a href="self1.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="footer">
<p><span class="bleft"><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="bright">Last updated on: August 5, 2005</span></p>
</div>
</body>
</html>