80 lines
5.9 KiB
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80 lines
5.9 KiB
HTML
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function APPLY</TITLE>
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<A NAME="apply"><I>Function</I> <B>APPLY</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>apply</B> <I>function <TT>&rest</TT> args+</I> => <I><I>result</I><B>*</B></I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>function</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#function_designator"><I>function designator</I></A>. <P>
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<I>args</I>---a <A REL=DEFINITION HREF="26_glo_s.htm#spreadable_argument_list_designator"><I>spreadable argument list designator</I></A>. <P>
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<I>results</I>---the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> returned by <I>function</I>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_a.htm#apply"><I>Applies</I></A> the <I>function</I> to the <I>args</I>. <P>
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When the <I>function</I> receives its arguments via <TT>&rest</TT>, it is permissible (but not required) for the <A REL=DEFINITION HREF="26_glo_i.htm#implementation"><I>implementation</I></A> to <A REL=DEFINITION HREF="26_glo_b.htm#bind"><I>bind</I></A> the <A REL=DEFINITION HREF="26_glo_r.htm#rest_parameter"><I>rest parameter</I></A> to an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> that shares structure with the last argument to <A REL=DEFINITION HREF="#apply"><B>apply</B></A>. Because a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> can neither detect whether it was called via <A REL=DEFINITION HREF="#apply"><B>apply</B></A> nor whether (if so) the last argument to <A REL=DEFINITION HREF="#apply"><B>apply</B></A> was a <A REL=DEFINITION HREF="26_glo_c.htm#constant"><I>constant</I></A>, <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming programs</I></A> must neither rely on the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> structure of a <A REL=DEFINITION HREF="26_glo_r.htm#rest_list"><I>rest list</I></A> to be freshly consed, nor modify that <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> structure. <P>
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<A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> can be used with <A REL=DEFINITION HREF="#apply"><B>apply</B></A> in certain circumstances; see <A REL=CHILD HREF="05_abe.htm">Section 5.1.2.5 (APPLY Forms as Places)</A>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(setq f '+) => +
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(apply f '(1 2)) => 3
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(setq f #'-) => #<FUNCTION ->
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(apply f '(1 2)) => -1
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(apply #'max 3 5 '(2 7 3)) => 7
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(apply 'cons '((+ 2 3) 4)) => ((+ 2 3) . 4)
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(apply #'+ '()) => 0
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(defparameter *some-list* '(a b c))
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(defun strange-test (&rest x) (eq x *some-list*))
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(apply #'strange-test *some-list*) => <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent">implementation-dependent</A>
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(defun bad-boy (&rest x) (rplacd x 'y))
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(bad-boy 'a 'b 'c) has undefined consequences.
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(apply #'bad-boy *some-list*) has undefined consequences.
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</PRE>
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</TT> <P>
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<PRE>
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(defun foo (size &rest keys &key double &allow-other-keys)
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(let ((v (apply #'make-array size :allow-other-keys t keys)))
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(if double (concatenate (type-of v) v v) v)))
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(foo 4 :initial-contents '(a b c d) :double t)
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=> #(A B C D A B C D)
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B> None.
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<P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f_funcal.htm#funcall"><B>funcall</B></A>, <A REL=DEFINITION HREF="f_fdefin.htm#fdefinition"><B>fdefinition</B></A>, <A REL=DEFINITION HREF="s_fn.htm#function"><B>function</B></A>, <A REL=CHILD HREF="03_a.htm">Section 3.1 (Evaluation)</A>, <A REL=CHILD HREF="05_abe.htm">Section 5.1.2.5 (APPLY Forms as Places)</A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss297.htm">REST-LIST-ALLOCATION:MAY-SHARE</A><LI> <A REL=CHILD HREF="../Issues/iss179.htm">FUNCTION-TYPE:X3J13-MARCH-88</A><P></UL><HR>
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