84 lines
7.9 KiB
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84 lines
7.9 KiB
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<!-- 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 UNION, NUNION</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_subset.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="15_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="union"><A NAME="nunion"><I>Function</I> <B>UNION, NUNION</B></A></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>union</B> <I>list-1 list-2 <TT>&key</TT> key test test-not</I> => <I>result-list</I><P>
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<B>nunion</B> <I>list-1 list-2 <TT>&key</TT> key test test-not</I> => <I>result-list</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>list-1</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_list"><I>proper list</I></A>. <P>
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<I>list-2</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#proper_list"><I>proper list</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>result-list</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="#union"><B>union</B></A> and <A REL=DEFINITION HREF="#nunion"><B>nunion</B></A> return a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> that contains every element that occurs in either <I>list-1</I> or <I>list-2</I>. <P>
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For all possible ordered pairs consisting of one element from <I>list-1</I> and one element from <I>list-2</I>, <TT>:test</TT> or <TT>:test-not</TT> is used to determine whether they <A REL=DEFINITION HREF="26_glo_s.htm#satisfy_the_test"><I>satisfy the test</I></A>. The first argument to the <TT>:test</TT> or <TT>:test-not</TT> function is the part of the element of <I>list-1</I> extracted by the <TT>:key</TT> function (if supplied); the second argument is the part of the element of <I>list-2</I> extracted by the <TT>:key</TT> function (if supplied). <P>
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The argument to the <TT>:key</TT> function is an element of <I>list-1</I> or <I>list-2</I>; the return value is part of the supplied element. If <TT>:key</TT> is not supplied or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, the element of <I>list-1</I> or <I>list-2</I> itself is supplied to the <TT>:test</TT> or <TT>:test-not</TT> function. <P>
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For every matching pair, one of the two elements of the pair will be in the result. Any element from either <I>list-1</I> or <I>list-2</I> that matches no element of the other will appear in the result. <P>
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If there is a duplication between <I>list-1</I> and <I>list-2</I>, only one of the duplicate instances will be in the result. If either <I>list-1</I> or <I>list-2</I> has duplicate entries within it, the redundant entries might or might not appear in the result. <P>
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The order of elements in the result do not have to reflect the ordering of <I>list-1</I> or <I>list-2</I> in any way. The result <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> may be <A REL=DEFINITION HREF="f_eq.htm#eq"><B>eq</B></A> to either <I>list-1</I> or <I>list-2</I> if appropriate. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(union '(a b c) '(f a d))
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=> (A B C F D)
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OR=> (B C F A D)
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OR=> (D F A B C)
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(union '((x 5) (y 6)) '((z 2) (x 4)) :key #'car)
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=> ((X 5) (Y 6) (Z 2))
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OR=> ((X 4) (Y 6) (Z 2))
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(setq lst1 (list 1 2 '(1 2) "a" "b")
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lst2 (list 2 3 '(2 3) "B" "C"))
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=> (2 3 (2 3) "B" "C")
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(nunion lst1 lst2)
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=> (1 (1 2) "a" "b" 2 3 (2 3) "B" "C")
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OR=> (1 2 (1 2) "a" "b" "C" "B" (2 3) 3)
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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<A REL=DEFINITION HREF="#nunion"><B>nunion</B></A> is permitted to modify any part, <A REL=DEFINITION HREF="26_glo_c.htm#car"><I>car</I></A> or <A REL=DEFINITION HREF="26_glo_c.htm#cdr"><I>cdr</I></A>, of the <A REL=DEFINITION HREF="26_glo_l.htm#list_structure"><I>list structure</I></A> of <I>list-1</I> or <I>list-2</I>. <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-1</I> and <I>list-2</I> are not <A REL=DEFINITION HREF="26_glo_p.htm#proper_list"><I>proper lists</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_isec_.htm#intersection"><B>intersection</B></A>, <A REL=CHILD HREF="03_ba.htm">Section 3.2.1 (Compiler Terminology)</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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Since the <A REL=DEFINITION HREF="#nunion"><B>nunion</B></A> side effect is not required, it should not be used in for-effect-only positions in portable code. <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><LI> <A REL=CHILD HREF="../Issues/iss083.htm">CONSTANT-MODIFICATION:DISALLOW</A><LI> <A REL=CHILD HREF="../Issues/iss293.htm">REMF-DESTRUCTION-UNSPECIFIED:X3J13-MAR-89</A><P></UL><HR>
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