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+
+<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> |
+<a href="../tutorials/tutorials.htm">Tutorials</a> |
+<a href="../examples/examples.htm">Examples</a> |
+<a href="reference-index.htm">Reference</a>
+
+<hr>
+
+<h1>defmacro</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>(defmacro <i>symbol arg-list body</i>)</dt>
+<dd><i>symbol</i> - the name of the macro being defined<br>
+<i>arg-list</i> - a list of the formal arguments to the macro of the form:<br>
+<dl>
+<dd>([<i>arg1</i> ... ]<br>
+ [<a href="lambda-keyword-optional.htm">&optional</a> <i>oarg1</i> ... ]<br>
+ [<a href="lambda-keyword-rest.htm">&rest</a> <i>rarg</i>]<br>
+ [<a href="lambda-keyword-key.htm">&key</a> ... ]<br>
+ [<a href="lambda-keyword-aux.htm">&aux</a> <i>aux1</i> ... ])<br></dd>
+</dl>
+<i>body</i> - a series of LISP forms (expressions) that are executed in order.<br>
+returns - the macro <i>symbol</i></dd>
+</dl>
+
+<h2>Description</h2>
+
+<p>'defmacro' defines a macro expansion. When the 'symbol' name of the macro
+expansion is encountered [similar to a function invocation], the 'body' of
+code that was defined in the 'defmacro' is expanded and replaces the macro
+invocation.</p>
+
+<p>All of the 'argN' formal arguments that are defined are required to
+appear in the invocation of the macro expansion.</p>
+
+<p>If there are any
+<a href="lambda-keyword-optional.htm">&optional</a> arguments defined, they will
+be filled in order.</p>
+
+<p>If there is a <a href="lambda-keyword-rest.htm">&rest</a>
+argument defined, and all the required formal arguments and
+<a href="lambda-keyword-optional.htm">&optional</a> arguments are filled, any and
+all further parameters will be passed into the function via the 'rarg'
+argument. <b>Note</b> that there can be only one 'rarg' argument for
+<a href="lambda-keyword-rest.htm">&rest</a>.</p>
+
+<p>If there are insufficient parameters for any of the
+<a href="lambda-keyword-optional.htm">&optional</a> or
+<a href="lambda-keyword-rest.htm">&rest</a> arguments, they will contain
+<a href="nil.htm">NIL</a>.</p>
+
+<p>The <a href="lambda-keyword-aux.htm">&aux</a> variables are a mechanism
+for you to define variables local to the 'defmacro' execution. At the end of
+the function execution, these local symbols and their values are are
+removed.</p>
+
+<h2>Examples</h2>
+
+<pre class="example">
+(defmacro plus (num1 num2) <font color="#008844">; define PLUS macro</font>
+ `(+ ,num1 ,num2)) <font color="#008844">; which is a 2 number add</font>
+
+(plus 1 2) <font color="#008844">; returns 3</font>
+(setq x 10) <font color="#008844">; set x to 10</font>
+(setq y 20) <font color="#008844">; set y to 20</font>
+(plus x y) <font color="#008844">; returns 30</font>
+
+(defmacro betterplus (num &rest nlist) <font color="#008844">; define a BETTERPLUS macro</font>
+ `(+ ,num ,@nlist)) <font color="#008844">; which can take many numbers</font>
+
+(betterplus 1) <font color="#008844">; returns 1</font>
+(betterplus 1 2 3) <font color="#008844">; returns 6</font>
+(betterplus 1 2 3 4 5) <font color="#008844">; returns 15</font>
+
+(defmacro atest (x &optional y &rest z) <font color="#008844">; define ATEST macro</font>
+ (princ " x: ") (princ x) <font color="#008844">; \</font>
+ (princ " y: ") (princ y) <font color="#008844">; print out the parameters</font>
+ (princ " z: ") (princ z) (terpri) <font color="#008844">; / (un-evaluated)</font>
+ `(print (+ ,x ,y ,@z))) <font color="#008844">; add them together (eval'ed)</font>
+
+(atest 1) <font color="#008844">; prints - x: 1 y: NIL z: NIL</font>
+ <font color="#008844">; error: bad argument type</font>
+ <font color="#008844">; because (+ 1 NIL) isn't valid</font>
+(atest 1 2) <font color="#008844">; prints - x: 1 y: 2 z: NIL</font>
+ <font color="#008844">; returns 3</font>
+(atest 1 2 3) <font color="#008844">; prints - x: 1 y: 2 z: (3)</font>
+ <font color="#008844">; returns 6</font>
+(atest 1 2 3 4 5) <font color="#008844">; prints - x: 1 y: 2 z: (3 4 5)</font>
+ <font color="#008844">; returns 15</font>
+(setq a 99) <font color="#008844">; set A to 99</font>
+(setq b 101) <font color="#008844">; set B to 101</font>
+(atest a b) <font color="#008844">; prints - x: A y: B z: NIL</font>
+ <font color="#008844">; returns 200</font>
+(atest a b 9 10 11) <font color="#008844">; prints - x: A y: B z: (9 10 11)</font>
+ <font color="#008844">; returns 230</font>
+</pre>
+
+<p><b>Common Lisp:</b> Common Lisp supports an optional documentation
+string as the first form in the 'body' of a 'defmacro' or
+<a href="defun.htm">defun</a>. XLISP will accept this string
+as a valid form, but it will not do anything special with it.</p>
+
+<p>See the
+<a href="../manual/xlisp-man-013.htm#defmacro">defmacro</a>
+special form in the <nobr>XLISP 2.0</nobr> manual.</p>
+
+<p><nobr> <a href="#top">Back to Top</nobr></a></p>
+
+<hr>
+
+<a href="../start.htm">Nyquist / XLISP 2.0</a> -
+<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>
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