64 lines
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64 lines
4.6 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: Macro DESTRUCTURING-BIND</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="m_defpar.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_data_a.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="s_let_l.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="destructuring-bind"><I>Macro</I> <B>DESTRUCTURING-BIND</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>destructuring-bind</B> <I>lambda-list expression <I>declaration</I><B>*</B> <I>form</I><B>*</B></I><P> => <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>lambda-list</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#destructuring_lambda_list"><I>destructuring lambda list</I></A>. <P>
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<I>expression</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A>. <P>
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<I>declaration</I>---a <A REL=DEFINITION HREF="s_declar.htm#declare"><B>declare</B></A> <A REL=DEFINITION HREF="26_glo_e.htm#expression"><I>expression</I></A>; not evaluated. <P>
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<I>forms</I>---an <A REL=DEFINITION HREF="26_glo_i.htm#implicit_progn"><I>implicit progn</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 the <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</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="#destructuring-bind"><B>destructuring-bind</B></A> binds the variables specified in <I>lambda-list</I> to the corresponding values in the tree structure resulting from the evaluation of <I>expression</I>; then <A REL=DEFINITION HREF="#destructuring-bind"><B>destructuring-bind</B></A> evaluates <I>forms</I>. <P>
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The <I>lambda-list</I> supports destructuring as described in <A REL=CHILD HREF="03_de.htm">Section 3.4.5 (Destructuring Lambda Lists)</A>. <P>
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<P><B>Examples:</B><P>
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<PRE>
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(defun iota (n) (loop for i from 1 to n collect i)) ;helper
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(destructuring-bind ((a &optional (b 'bee)) one two three)
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`((alpha) ,@(iota 3))
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(list a b three two one)) => (ALPHA BEE 3 2 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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If the result of evaluating the <I>expression</I> does not match the destructuring pattern, an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_error.htm#error"><B>error</B></A> should be signaled. <P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="s_flet_.htm#macrolet"><B>macrolet</B></A>, <A REL=DEFINITION HREF="m_defmac.htm#defmacro"><B>defmacro</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 issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss130.htm">DESTRUCTURING-BIND:NEW-MACRO</A><LI> <A REL=CHILD HREF="../Issues/iss097.htm">DECLS-AND-DOC</A><P></UL><HR>
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