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<html><head><title>XLISP dolist</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
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<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>dolist</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>special form (fsubr)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xlcont.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(dolist (<i>symbol list-expr</i> [<i>result</i>]) [<i>expr</i> ... ])</dt>
<dd><i>symbol</i> - a symbol<br>
<i>list-expr</i> - a list expression<br>
<i>result</i> - an optional expression for the returned result<br>
<i>expr</i> - expressions comprising the body of the loop which may
contain <a href="return.htm">return</a>s,
<a href="go.htm">go</a>s or tags for
<a href="go.htm">go</a><br>
returns - the return value of the result expression or
<a href="nil.htm">NIL</a></dd>
</dl>
<h2>Description</h2>
<p> The 'dolist' special form is basically a list-oriented 'for' looping
construct that contains a loop 'symbol', a 'list-expr' to draw values from,
an optional 'return' value and a block of code [expressions] to evaluate.
The sequence of execution is:</p>
<pre>
<i>symbol</i> := CAR of <i>list-expr</i>
temp-list := CDR of <i>list-expr</i>
while temp-list is not empty
loop code execution
<i>symbol</i> := CAR of temp-list
temp-list := CDR of temp-list
end-while
return <i>result</i>
</pre>
<p>The main loop 'symbol' will take on successive values from 'list-expr'.
The 'dolist' form will go through and create and initialize the 'symbol'.
After execution of the loop 'exprs', the 'symbol' is set to the next value
in the 'list-expr'. This continues until the 'list-expr' has been exhausted.
The value of the 'result' expression is evaluated and returned. If no
'result' is specified, <a href="nil.htm">NIL</a> is returned.
When the 'dolist' is finished execution, the 'symbol' that was defined will
no longer exist or retain its value. If the 'list-expr' is an empty list,
then no loop execution takes place and the 'result' is returned.</p>
<h2>Examples</h2>
<pre class="example">
(dolist (i () "done") <font color="#008844">; DOLIST with I loop variable</font>
(print "here")) <font color="#008844">; an empty list</font>
<font color="#008844">; and a return value</font>
<font color="#008844">; returns "done"</font>
(dolist (x '(a b c) "fini") <font color="#008844">; DOLIST with X loop variable</font>
(princ x)) <font color="#008844">; a list with (A B C)</font>
<font color="#008844">; and a return value</font>
<font color="#008844">; prints ABC returns "fini"</font>
(dolist (y '(1 2 3)) <font color="#008844">; DOLIST with Y loop variable</font>
(princ (* y y))) <font color="#008844">; a list with (1 2 3)</font>
<font color="#008844">; and no return value</font>
<font color="#008844">; prints 149 returns NIL</font>
<font color="#008844">; returns "met in the middle"</font>
</pre>
<p>See the
<a href="../manual/xlisp-man-020.htm#dolist">dolist</a>
special form in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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