94 lines
2.8 KiB
HTML
94 lines
2.8 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> cond (MACRO)</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" cond (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="node88.html"><IMG ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A>
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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="node88.html"> cons (FUNCTION)</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="node86.html"> cdr (Function)</A>
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<BR> <HR> <P>
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<H1> cond (MACRO)</H1>
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<P>
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<b> Format:</b>
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<tt> (cond (<test1> <body1> )</tt>
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<tt> (<test2> <body2> )</tt>
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<tt> .</tt>
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<tt> .</tt>
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<tt> (<testN> <bodyN> ))</tt>
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<P>
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<b> Required arguments:</b>
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none
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<P>
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<b> Optional arguments:</b>
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zero or more <tt> (<test> <body> )</tt> clauses
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<P>
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Here, <tt> <test> </tt> is any Lisp expression. The <tt> <body> </tt> is a sequence of zero or more Lisp expressions.
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<P>
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Each <tt> <test> </tt> expression is evaluated in turn, until one is
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found whose value is non-NIL. For this clause, the sequence of
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<tt> <body> </tt> expressions are evaluated and the value of the last
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expression is returned as the result of cond. If no successful
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<tt> <test> </tt> expression is found, cond returns NIL. If a successful
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<tt> <test> </tt> expression is found, but its clause contains no <tt> <body> </tt>
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expressions, the result of the <tt> <test> </tt> expression is returned as
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the result of cond.
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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>> (setq a '3)
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3
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> (setq b '4)
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4
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> (cond ((= a b) 'equal)
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((< a b) 'b-is-bigger)
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(t 'a-is-bigger))
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B-IS-BIGGER
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> (setq action 'square-both)
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SQUARE-BOTH
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> (cond ((equal action 'clear-both)
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(setq a 0)
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(setq b 0))
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((equal action 'square-both)
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(setq a (* a a))
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(setq b (* b b)))
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((equal action 'square-a)
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(setq a (* a a)))
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((equal action 'square-b)
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(setq b (* b b))))
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16
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> (cond ((= a 5) 'found)
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((= b 5) 'found))
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NIL
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> (cond ((+ a 1))) ; strange use of cond
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10 ; before this, a was 9 due to previous
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; cond clauses
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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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