78 lines
5.2 KiB
HTML
78 lines
5.2 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 COPY-TREE</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_car_c.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_sublis.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="copy-tree"><I>Function</I> <B>COPY-TREE</B></A> <P>
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<P>
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<P><B>Syntax:</B><P>
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<P>
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<B>copy-tree</B> <I>tree</I> => <I>new-tree</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>tree</I>---a <A REL=DEFINITION HREF="26_glo_t.htm#tree"><I>tree</I></A>. <P>
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<I>new-tree</I>---a <A REL=DEFINITION HREF="26_glo_t.htm#tree"><I>tree</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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Creates a <A REL=DEFINITION HREF="26_glo_c.htm#copy"><I>copy</I></A> of a <A REL=DEFINITION HREF="26_glo_t.htm#tree"><I>tree</I></A> of <A REL=DEFINITION HREF="26_glo_c.htm#cons"><I>conses</I></A>. <P>
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If <I>tree</I> is not a <A REL=DEFINITION HREF="26_glo_c.htm#cons"><I>cons</I></A>, it is returned; otherwise, the result is a new <A REL=DEFINITION HREF="26_glo_c.htm#cons"><I>cons</I></A> of the results of calling <A REL=DEFINITION HREF="#copy-tree"><B>copy-tree</B></A> on the <A REL=DEFINITION HREF="26_glo_c.htm#car"><I>car</I></A> and <A REL=DEFINITION HREF="26_glo_c.htm#cdr"><I>cdr</I></A> of <I>tree</I>. In other words, all <A REL=DEFINITION HREF="26_glo_c.htm#cons"><I>conses</I></A> in the <A REL=DEFINITION HREF="26_glo_t.htm#tree"><I>tree</I></A> represented by <I>tree</I> are copied recursively, stopping only when non-<A REL=DEFINITION HREF="26_glo_c.htm#cons"><I>conses</I></A> are encountered. <P>
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<A REL=DEFINITION HREF="#copy-tree"><B>copy-tree</B></A> does not preserve circularities and the sharing of substructure. <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 object (list (cons 1 "one")
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(cons 2 (list 'a 'b 'c))))
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=> ((1 . "one") (2 A B C))
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(setq object-too object) => ((1 . "one") (2 A B C))
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(setq copy-as-list (copy-list object))
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(setq copy-as-alist (copy-alist object))
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(setq copy-as-tree (copy-tree object))
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(eq object object-too) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(eq copy-as-tree object) => <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
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(eql copy-as-tree object) => <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
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(equal copy-as-tree object) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(setf (first (cdr (second object))) "a"
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(car (second object)) "two"
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(car object) '(one . 1)) => (ONE . 1)
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object => ((ONE . 1) ("two" "a" B C))
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object-too => ((ONE . 1) ("two" "a" B C))
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copy-as-list => ((1 . "one") ("two" "a" B C))
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copy-as-alist => ((1 . "one") (2 "a" B C))
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copy-as-tree => ((1 . "one") (2 A B C))
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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> 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_tree_e.htm#tree-equal"><B>tree-equal</B></A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss138.htm">DOTTED-LIST-ARGUMENTS:CLARIFY</A><P></UL><HR>
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