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39 lines
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<TITLE>CLHS: Section 3.4.4.1</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="03_dd.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="03_dd.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="03_ddaa.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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3.4.4.1 Destructuring by Lambda Lists</H2> <P>
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Anywhere in a <A REL=DEFINITION HREF="26_glo_m.htm#macro_lambda_list"><I>macro lambda list</I></A> where a parameter name can appear, and where <A REL=DEFINITION HREF="26_glo_o.htm#ordinary_lambda_list"><I>ordinary lambda list</I></A> syntax (as described in <A REL=CHILD HREF="03_da.htm">Section 3.4.1 (Ordinary Lambda Lists)</A>) does not otherwise allow a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>, a <A REL=DEFINITION HREF="26_glo_d.htm#destructuring_lambda_list"><I>destructuring lambda list</I></A> can appear in place of the parameter name. When this is done, then the argument that would match the parameter is treated as a (possibly dotted) <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A>, to be used as an argument list for satisfying the parameters in the embedded <A REL=DEFINITION HREF="26_glo_l.htm#lambda_list"><I>lambda list</I></A>. This is known as destructuring. <P>
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Destructuring is the process of decomposing a compound <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> into its component parts, using an abbreviated, declarative syntax, rather than writing it out by hand using the primitive component-accessing functions. Each component part is bound to a variable. <P>
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A destructuring operation requires an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> to be decomposed, a pattern that specifies what components are to be extracted, and the names of the variables whose values are to be the components. <P>
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<A REL=CHILD HREF="03_ddaa.htm"><H2>
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3.4.4.1.1 Data-directed Destructuring by Lambda Lists</H2></A><P>
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<A REL=CHILD HREF="03_ddab.htm"><H2>
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3.4.4.1.2 Lambda-list-directed Destructuring by Lambda Lists</H2></A><P><P>
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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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