summaryrefslogtreecommitdiff
path: root/docsrc/xlisp/xlisp-doc/reference/let-star.htm
diff options
context:
space:
mode:
Diffstat (limited to 'docsrc/xlisp/xlisp-doc/reference/let-star.htm')
-rw-r--r--docsrc/xlisp/xlisp-doc/reference/let-star.htm106
1 files changed, 106 insertions, 0 deletions
diff --git a/docsrc/xlisp/xlisp-doc/reference/let-star.htm b/docsrc/xlisp/xlisp-doc/reference/let-star.htm
new file mode 100644
index 0000000..f6ac98a
--- /dev/null
+++ b/docsrc/xlisp/xlisp-doc/reference/let-star.htm
@@ -0,0 +1,106 @@
+<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>&nbsp; -&nbsp;
+<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>let*</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>(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 &amp; 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 &amp; 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>&nbsp;&nbsp;<a href="#top">Back to Top</nobr></a></p>
+
+<hr>
+
+<a href="../start.htm">Nyquist / XLISP 2.0</a>&nbsp; -&nbsp;
+<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>
+
+</body></html> \ No newline at end of file