docsrc/xlisp/xlisp-doc/reference/loop.htm


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<html><head><title>XLISP loop</title>

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<h1>loop</h1>

<hr>

<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
  <td><nobr>Type:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>special form (fsubr)</nobr></td>
</tr>
<tr valign="top">
  <td><nobr>Source:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>xlcont.c</nobr></td>
</tr>
</tbody></table></p>

<h2>Syntax</h2>

<dl>
<dt>(loop <i>body</i> ... )</dt>
<dd><i>body</i> - a series of expressions<br>
returns - never returns [must use non-local exit]</dd>
</dl>

<h2>Description</h2>

<p>The 'loop' special form specifies a 'repeat-forever' construct. The
expressions in'body' will be evaluated. When the last expression is
evaluated in 'body', 'loop' will then repeat the 'body'. When a
<a href="return.htm">return</a> is evaluated within a 'loop', the
specified value will be returned. 'loop' itself does not generate a return
value. Other exit mechanisms include
<nobr><a href="go.htm">go</a> ,</nobr>
<nobr><a href="throw.htm">throw</a> ,</nobr>
<nobr><a href="return-from.htm">return-from</a> and errors.</p>

<h2>Examples</h2>

<pre class="example">
(setq i 65)                      <font color="#008844">; initial value</font>

(loop                            <font color="#008844">; LOOP</font>
  (princ (int-char i))           <font color="#008844">;   print the character</font>
  (if (= i 90) (return "done"))  <font color="#008844">;   test for limit</font>
  (setq i (1+ i)))               <font color="#008844">;   increment and repeat</font>
                                 <font color="#008844">; prints ABCDEFGHIJKLMNOPQRSTUVWXYZ</font>
                                 <font color="#008844">; returns "done"</font>
</pre>

<p><b>Note:</b> If you create a 'loop' with no exit mechanism, you will
probably have to abort your XLISP session.</p>

<p>See the
<a href="../manual/xlisp-man-020.htm#loop">loop</a>
special form in the <nobr>XLISP 2.0</nobr> manual.</p>

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