94 lines
2.6 KiB
HTML
94 lines
2.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Originally converted to HTML using LaTeX2HTML 95 (Thu Jan 19 1995) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE> defun (MACRO)</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" defun (MACRO)">
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<meta name="keywords" value="lp">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<BR> <HR>
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<A HREF="node90.html"><IMG ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A>
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<A HREF="node72.html"><IMG ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A>
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<A HREF="node88.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif"></A> <BR>
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<A HREF="lp.html"><B>Contents</B></A>
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<B> Next:</B>
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<A HREF="node90.html"> do (SPECIAL FORM)</A>
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<B>Up:</B>
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<A HREF="node72.html"> Appendix: Selected Lisp </A>
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<B> Previous:</B>
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<A HREF="node88.html"> cons (FUNCTION)</A>
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<BR> <HR> <P>
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<H1> defun (MACRO)</H1>
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<P>
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<b> Format:</b>
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<tt> (defun <name> (<par1> <par2> ... <parN> )</tt>
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<tt> <body> )</tt>
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<P>
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<b> Required arguments:</b>
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2
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<P>
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<tt> <name> </tt>: a symbol which is appropriate as the name of function;
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<tt> (<par1> <par2> ...)</tt>: a list of zero or more symbols which
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are appropriate as parameter names
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<P>
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<b> Optional arguments:</b>
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1
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<P>
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<tt> <body> </tt>: a sequence of zero or more Lisp expressions
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<P>
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The arguments to defun are not evaluated---they are used to establish a procedure definition. The first argument is a
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symbol which specifies the name of the function. This name can
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later be used to execute the <tt> <body> </tt> of the function. The
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parameter-list follows the name. This list specifies the number and order of
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arguments in a function call. Each <tt> <par> </tt> is symbol which may appear
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in the <tt> <body> </tt>. The value of each parameter, <tt> <par> </tt>, is
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determined by the value of corresponding argument in the function call.
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defun returns the name of the function.
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<P>
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<b> Examples:</b>
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<P>
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<BLOCKQUOTE>
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<PRE>> (defun square (x)
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(* x x))
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SQUARE
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> (square 4)
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16
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> (square (+ 7 -2))
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25
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> (defun equal-length (lst1 lst2)
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(cond ((= (length lst1) (length lst2)) t)
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(t nil)))
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EQUAL-LENGTH
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> (equal-length '(a b c) '((d e) f g))
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T
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> (equal-length '() (rest '(a b)))
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NIL
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> (defun side-effect (x y)
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(setq x (* x x x))
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(+ x y))
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SIDE-EFFECT
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> (side-effect 2 3)
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11
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> (side-effect -4 14)
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-50
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</PRE>
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</BLOCKQUOTE>
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<P>
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<BR> <HR>
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<P>
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<ADDRESS>
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<I>© Colin Allen & Maneesh Dhagat <BR>
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March 2007 </I>
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</ADDRESS>
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</BODY>
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