74 lines
5.7 KiB
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74 lines
5.7 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 ADJOIN</TITLE>
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<A NAME="adjoin"><I>Function</I> <B>ADJOIN</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>adjoin</B> <I>item list <TT>&key</TT> key test test-not</I> => <I>new-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>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>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>new-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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Tests whether <I>item</I> is the same as an existing element of <I>list</I>. If the <I>item</I> is not an existing element, <A REL=DEFINITION HREF="#adjoin"><B>adjoin</B></A> adds it to <I>list</I> (as if by <A REL=DEFINITION HREF="f_cons.htm#cons"><B>cons</B></A>) and returns the resulting <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>; otherwise, nothing is added and the original <I>list</I> is returned. <P>
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The <I>test</I>, <I>test-not</I>, and <I>key</I> affect how it is determined whether <I>item</I> is the same as an <A REL=DEFINITION HREF="26_glo_e.htm#element"><I>element</I></A> of <I>list</I>. For details, see <A REL=CHILD HREF="17_ba.htm">Section 17.2.1 (Satisfying a Two-Argument Test)</A>.<P>
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<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 slist '()) => NIL
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(adjoin 'a slist) => (A)
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slist => NIL
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(setq slist (adjoin '(test-item 1) slist)) => ((TEST-ITEM 1))
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(adjoin '(test-item 1) slist) => ((TEST-ITEM 1) (TEST-ITEM 1))
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(adjoin '(test-item 1) slist :test 'equal) => ((TEST-ITEM 1))
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(adjoin '(new-test-item 1) slist :key #'cadr) => ((TEST-ITEM 1))
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(adjoin '(new-test-item 1) slist) => ((NEW-TEST-ITEM 1) (TEST-ITEM 1))
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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><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="m_pshnew.htm#pushnew"><B>pushnew</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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<PRE>
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(adjoin item list :key fn)
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== (if (member (fn item) list :key fn) list (cons item list))
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</PRE>
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</TT> <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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