86 lines
7.1 KiB
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86 lines
7.1 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 MEMBER, MEMBER-IF, MEMBER-IF-NOT</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_rest.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_conses.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_mapc_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="member"><A NAME="member-if"><A NAME="member-if-not"><I>Function</I> <B>MEMBER, MEMBER-IF, MEMBER-IF-NOT</B></A></A></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>member</B> <I>item list <TT>&key</TT> key test test-not</I> => <I>tail</I><P>
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<B>member-if</B> <I>predicate list <TT>&key</TT> key</I> => <I>tail</I><P>
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<B>member-if-not</B> <I>predicate list <TT>&key</TT> key</I> => <I>tail</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>item</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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<I>list</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_list"><I>proper list</I></A>. <P>
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<I>predicate</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of one <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A> that returns a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>. <P>
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<I>test</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of two <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> that returns a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>. <P>
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<I>test-not</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of two <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> that returns a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>. <P>
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<I>key</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of one argument, or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<I>tail</I>---a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#member"><B>member</B></A>, <A REL=DEFINITION HREF="#member-if"><B>member-if</B></A>, and <A REL=DEFINITION HREF="#member-if-not"><B>member-if-not</B></A> each search <I>list</I> for <I>item</I> or for a top-level element that <I>satisfies the test</I>. The argument to the <I>predicate</I> function is an element of <I>list</I>. <P>
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If some element <I>satisfies the test</I>, the tail of <I>list</I> beginning with this element is returned; otherwise <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> is returned. <P>
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<I>list</I> is searched on the top level only. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(member 2 '(1 2 3)) => (2 3)
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(member 2 '((1 . 2) (3 . 4)) :test-not #'= :key #'cdr) => ((3 . 4))
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(member 'e '(a b c d)) => NIL
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</PRE>
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</TT> <P>
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<PRE>
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(member-if #'listp '(a b nil c d)) => (NIL C D)
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(member-if #'numberp '(a #\Space 5/3 foo)) => (5/3 FOO)
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(member-if-not #'zerop
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'(3 6 9 11 . 12)
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:key #'(lambda (x) (mod x 3))) => (11 . 12)
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B> None.
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<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><P>
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<P>
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Should be prepared to signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>list</I> is not a <A REL=DEFINITION HREF="26_glo_p.htm#proper_list"><I>proper list</I></A>. <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_find_.htm#find"><B>find</B></A>, <A REL=DEFINITION HREF="f_pos_p.htm#position"><B>position</B></A>, <A REL=CHILD HREF="03_f.htm">Section 3.6 (Traversal Rules and Side Effects)</A> <P>
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<P><B>Notes:</B><P>
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<P>
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The <TT>:test-not</TT> parameter is deprecated. <P>
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The <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="#member-if-not"><B>member-if-not</B></A> is deprecated. <P>
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In the following <P>
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<PRE>
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(member 'a '(g (a y) c a d e a f)) => (A D E A F)
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</PRE>
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</TT> <P>
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the value returned by <A REL=DEFINITION HREF="#member"><B>member</B></A> is <A REL=DEFINITION HREF="26_glo_i.htm#identical"><I>identical</I></A> to the portion of the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> beginning with <TT>a</TT>. Thus <A REL=DEFINITION HREF="f_rplaca.htm#rplaca"><B>rplaca</B></A> on the result of <A REL=DEFINITION HREF="#member"><B>member</B></A> can be used to alter the part of the <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> where <TT>a</TT> was found (assuming a check has been made that <A REL=DEFINITION HREF="#member"><B>member</B></A> did not return <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>). <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/iss345.htm">TEST-NOT-IF-NOT:FLUSH-ALL</A><LI> <A REL=CHILD HREF="../Issues/iss240.htm">MAPPING-DESTRUCTIVE-INTERACTION:EXPLICITLY-VAGUE</A><P></UL><HR>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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