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<html><head><title>XLISP delete</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>delete</h1>
<hr>
<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
<td><nobr>Type:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>function (subr)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xllist.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(delete <i>expr list</i> [{:test | :test-not} <i>test</i>])</dt>
<dd><i>expr</i> - the expression to delete from <i>list</i><br>
<i>list</i> - the list to destructively modify<br>
<i>test</i> - optional test function (default is <a href="eql.htm">eql</a>)<br>
returns - the list with the matching expressions deleted</dd>
</dl>
<h2>Description</h2>
<p>The 'delete' function destructively modifies the 'list' by removing the
'expr'. The destructive aspect of this operation means that the actual
symbol value is used in the list-modifying operations, not a copy. If 'expr'
appears multiple times in the 'list', all occurances will be removed.</p>
<p>'list' must evaluate to a valid list. An atom for 'list' will result in
an error:</p>
<pre class="example">
<font color="#AA0000">error: bad argument type</font>
</pre>
<p>Having <a href="nil.htm">NIL</a> for 'list' will return a
<a href="nil.htm">NIL</a> as the result. You may specify your own
test with the ':test' and ':test-not' keywords.</p>
<h2>Examples</h2>
<pre class="example">
(delete 'b NIL) <font color="#008844">; returns NIL</font>
(delete 'b '(a b b c b)) <font color="#008844">; returns (A C)</font>
(setq a '(1 2 3)) (setq b a) <font color="#008844">; set up A and B</font>
(delete '2 a) <font color="#008844">; returns (1 3)</font>
(print a) <font color="#008844">; prints (1 3) A IS MODIFIED!</font>
(print b) <font color="#008844">; prints (1 3) B IS MODIFIED!</font>
(delete '(b) '((a)(b)(c))) <font color="#008844">; returns ((A) (B) (C))</font>
<font color="#008844">; EQL doesn't work on lists</font>
(delete '(b) '((a)(b)(c)) :test 'equal) <font color="#008844">; returns ((A) (C))</font>
</pre>
<p><b>Note:</b> The 'delete' function can work with a list or string as the
'expr'. However, the default <a href="eql.htm">eql</a> test does
not work with lists or strings, only symbols and numbers. To make this work,
you need to use the ':test' keyword along with
<a href="equal.htm">equal</a> for 'test'.</p>
<p><b>Common Lisp:</b> XLISP does not support the ':from-end', ':start',
':end', ':count' and ':key' keywords which Common Lisp does.</p>
<p>See the
<a href="../manual/xlisp-man-017.htm#delete">delete</a>
function in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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