59 lines
1.8 KiB
HTML
59 lines
1.8 KiB
HTML
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<!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> Apply</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" Apply">
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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="node69.html"><IMG ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A>
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<A HREF="node64.html"><IMG ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A>
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<A HREF="node67.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="node69.html"> Mapcar</A>
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<B>Up:</B>
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<A HREF="node64.html"> FunctionsLambda Expressions, </A>
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<B> Previous:</B>
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<A HREF="node67.html"> Funcall</A>
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<BR> <HR> <P>
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<H1> Apply</H1>
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<P>
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Apply takes its first argument and applies it as a function to the
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list of items making up the last. For example:
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<pre>
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>(apply '* '(1 2 3 4))
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24
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</pre>
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You can imagine this being obtained by constructing the list <tt>(* 1
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2 3 4)</tt> and evaluating the resulting list, although this is not
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strictly what happens since <tt>apply</tt> is a function, not a <a
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href="node71.html">macro</a>. Apply also allows intermediate arguments
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between the first and the last (see <a href="node81.html">appendix</a>)
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but the last argument is required to be a list.
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<p>
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Apply can also be used in conjunction with lambda lists. For example:
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<pre>
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>(apply '(lambda (x y) (* x y)) '(45 67))
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3015
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</pre>
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If this does not seem particularly useful to you, think about how it
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can be used to construct complex programs on the fly.
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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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May 1999</I>
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</ADDRESS>
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</BODY>
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