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<html><head><title>XLISP subst</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>subst</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>(subst <i>new-expr old-expr expr</i> [{:test | :test-not} <i>test</i>])</dt>
<dd><i>old-expr</i> - the expression to search for<br>
<i>new-expr</i> - the expression to replace <i>old-expr</i> with<br>
<i>expr</i> - the expression to substitute within, an atom or list<br>
<i>test</i> - optional test function, default is <a href="eql.htm">eql</a><br>
returns - the expression with substitutions</dd>
</dl>
<h2>Description</h2>
<p>The 'subst' function searches through an 'expr' and replaces each of the
'old-expr' elements with the 'new-expr'. The 'expr' with the substitutions,
if any, is returned. You may specify your own test with the ':test' and
':test-not' keywords followed by the 'test' you wish to perform.</p>
<h2>Examples</h2>
<pre class="example">
(subst 'new 'old '(old mid dif)) <font color="#008844">; returns (NEW MID DIF)</font>
(subst '(a) 'old '(old mid dif)) <font color="#008844">; returns ((A) MID DIF)</font>
(subst "a" 'old '(old mid dif)) <font color="#008844">; returns ("a" MID DIF)</font>
(defun mytest (x y) (princ x) (princ " ") <font color="#008844">; define a test function</font>
(princ y) (terpri) <font color="#008844">; that prints the arguments</font>
T ) <font color="#008844">; and always returns T</font>
(subst 'a 'b '(a b c d) :test 'mytest) <font color="#008844">; prints (A B C D) B returns A</font>
(subst 'a 'b '(a b) :test-not 'mytest) <font color="#008844">; prints (A B) B</font>
<font color="#008844">; A B</font>
<font color="#008844">; (B) B</font>
<font color="#008844">; B B</font>
<font color="#008844">; NIL B returns (A B)</font>
</pre>
<p><b>Note:</b> The 'subst' 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> Common Lisp supports the use of the ':key' keyword
which specifies a function that is applied to each element of 'expr' before
it is tested. XLISP does not support this.</p>
<p>See the
<a href="../manual/xlisp-man-016.htm#subst">subst</a>
function in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
<hr>
<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>
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