67 lines
1.9 KiB
HTML
67 lines
1.9 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> butlast (FUNCTION)</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" butlast (FUNCTION)">
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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="node84.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="node82.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="node84.html"> car (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="node82.html"> atom (PREDICATE)</A>
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<BR> <HR> <P>
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<H1> butlast (FUNCTION)</H1>
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<P>
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<b> Format:</b>
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<tt> (butlast <list> )</tt>
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<tt> (butlast <list> <int> )</tt>
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<P>
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<b> Required arguments:</b>
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1
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<P>
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First argument must evaluate to a list
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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> <int> </tt> must evaluate to an integer
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<P>
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If butlast is used with a single argument then it is equivalent to <tt> (reverse (rest (reverse <list> )))</tt>. I.e. it will return the list argument with the last element removed.
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<P>
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If butlast is given an integer second argument, it is equivalent to <tt> (reverse (nthcdr <num> (reverse <list> )))</tt>. I.e. it will remove the number of elements specified from the end of the list.
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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>> (butlast '(a s d f))
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(A S D)
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> (butlast '(a s d f) 2)
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(A S)
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> (butlast '(a s d f) 0)
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(A S D F)
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> (reverse (nthcdr 2 (reverse '(a s d f))))
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(A S)
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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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