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<html><head><title>XLISP funcall</title>
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</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
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<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>funcall</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>xlbfun.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(funcall <i>function</i> [<i>arg1</i> ... ])</dt>
<dd><i>function</i> - the function or symbol to be called<br>
<i>argN</i> - an argument to be passed to <i>function</i><br>
returns - the result of calling the function with the arguments</dd>
</dl>
<h2>Description</h2>
<p>The 'funcall' function calls a function with a series of arguments.
It returns the result from calling the function with the arguments.</p>
<h2>Examples</h2>
<pre class="example">
(funcall '+ 1 2 3 4) <font color="#008844">; returns 10</font>
(funcall #'+ 1 2 3 4) <font color="#008844">; returns 10</font>
(funcall '+ '1 '2 '3) <font color="#008844">; returns 6</font>
(setq sys-add (function +)) <font color="#008844">; returns #<Subr-+: #22c32></font>
(setq a 99)
(funcall sys-add 1 a) <font color="#008844">; 100</font>
(funcall sys-add 1 'a) <font color="#008844">; error: bad argument type</font>
<font color="#008844">; you can't add a symbol, only it's value</font>
(setq a 2) <font color="#008844">; set A</font>
(setq b 3) <font color="#008844">; and B values</font>
(funcall (if (< a b) (function +) <font color="#008844">; 'function' can be computed</font>
(function -))
a b) <font color="#008844">; returns 5</font>
(defun add-to-list (arg list) <font color="#008844">; add a list or an atom</font>
(funcall (if (atom arg) 'cons <font color="#008844">; to the front of a list</font>
'append)
arg list))
(add-to-list 'a '(b c)) <font color="#008844">; returns (A B C)</font>
(add-to-list '(a b) '(b c)) <font color="#008844">; returns (A B B C)</font>
</pre>
<h2>Notes</h2>
<p>In XLISP, a '<nobr>special form</nobr>' of type FSUBR is not a function.
This means that 'funcall' only works with functions of type SUBR
<nobr>[built-in</nobr> function] or CLOSURE [function defined by
<a href="defun.htm">defun</a>, <a href="flet.htm">flet</a>,
<a href="labels.htm">labels</a>, or <a href="lambda.htm">lambda</a>], but
with special forms of <nobr>type FSUBR</nobr> a 'bad function' error is
signalled. Here is an example how to work around this behaviour:</p>
<pre class="example">
(defun <font color="#0000CC">funcall*</font> (function &rest args)
(if (eq (type-of function) 'fsubr)
(eval (cons function args))
(apply function args)))
</pre>
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