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<html><head><title>XLISP let*</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> |
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<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>let*</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>(let* ([<i>binding</i> ... ]) <i>expr</i> ... )</dt>
<dd><i>binding</i> - a variable binding which is one of the forms:
<dl>
<dd><i>symbol</i><br>
(<i>symbol init-expr</i>)
<dl>
<dd><i>symbol</i> - a symbol<br>
<i>init-expr</i> - an initialization expression for <i>symbol</i></dd>
</dl></dd></dl>
<i>expr</i> - an expression<br>
returns - the value of the last expression</dd>
</dl>
<h2>Description</h2>
<p>The 'let*' special form is basically a local block construct that
contains symbols [with optional initializations] and a block of code
[expressions] to evaluate. The first form after the 'let*' is the 'binding'
form. It contains a series of 'symbols' or 'bindings'. The 'binding' is a
'symbol' followed by an initialization expression 'init-expr'. If there is
no 'init-expr', the 'symbol' will be initialized to
<a href="nil.htm">NIL</a>. The execution of the bindings will
occur from the first to the last binding. The 'let*' form will go through
and create and initialize the symbols and then sequentially execute the
'exprs'. The value of the last 'expr' evaluated is returned. When the 'let*'
is finished execution, the 'symbols' that were defined will no longer exist
or retain their values.</p>
<h2>Examples</h2>
<pre class="example">
(let* (x y z) <font color="#008844">; LET* with local vars</font>
(print x) (print y) (print z)) <font color="#008844">; prints NIL NIL NIL</font>
(let* ((a 1) (b 2) (c 3)) <font color="#008844">; LET* with local vars & init</font>
(print (+ a b c))) <font color="#008844">; prints and returns 6</font>
(let* ((a 1) (b 2) (c (+ a b))) <font color="#008844">; LET* with local vars & init</font>
(print (+ a b c))) <font color="#008844">; prints and returns 6</font>
</pre>
<p><b>Note:</b></p>
<pre class="example">
(let* (a b) ... )
</pre>
<p>can be understood as:</p>
<pre class="example">
(let (a)
(let (b)
... ))
</pre>
<p>See the
<a href="../manual/xlisp-man-019.htm#let*">let*</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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