42 lines
3.9 KiB
HTML
42 lines
3.9 KiB
HTML
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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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<HTML>
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<HEAD>
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<TITLE>CLHS: Section 5.1.2.9</TITLE>
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<LINK HREF="../Data/clhs.css" REL="stylesheet" TYPE="text/css" />
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<META HTTP-EQUIV="Author" CONTENT="Kent M. Pitman">
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<META HTTP-EQUIV="Organization" CONTENT="LispWorks Ltd.">
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<LINK REL=NEXT HREF="05_ac.htm">
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</HEAD>
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<BODY>
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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="05_abh.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="05_ab.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="05_ac.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<HR>
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<H2>
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5.1.2.9 Other Compound Forms as Places</H2> <P>
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For any other <A REL=DEFINITION HREF="26_glo_c.htm#compound_form"><I>compound form</I></A> for which the <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operator</I></A> is a <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> <I>f</I>, the <A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> expands into a call to the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> named <TT>(setf </TT><I>f</I><TT>)</TT>. The first <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A> in the newly constructed <A REL=DEFINITION HREF="26_glo_f.htm#function_form"><I>function form</I></A> is <I>newvalue</I> and the remaining <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> are the remaining <A REL=DEFINITION HREF="26_glo_e.htm#element"><I>elements</I></A> of <I>place</I>. This expansion occurs regardless of whether <I>f</I> or <TT>(setf </TT><I>f</I><TT>)</TT> is defined as a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> locally, globally, or not at all. For example, <P>
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<TT>(setf (</TT><I>f</I><TT> </TT><I>arg1</I><TT> </TT><I>arg2</I><TT> ...) </TT><I>new-value</I><TT>)</TT> <P>
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expands into a form with the same effect and value as <P>
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<PRE>
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(let ((#:temp-1 arg1) ;force correct order of evaluation
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(#:temp-2 arg2)
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...
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(#:temp-0 new-value))
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(funcall (function (setf f)) #:temp-0 #:temp-1 #:temp-2...))
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</PRE>
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</TT> <P>
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A <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> named <TT>(setf </TT><I>f</I><TT>)</TT> must return its first argument as its only value in order to preserve the semantics of <A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A>. <P>
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<P>
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<HR>
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<A REL=NAVIGATOR HREF="../Front/StartPts.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Starting Points]" SRC="../Graphics/StartPts.gif" ALIGN=Bottom></A><A REL=TOC HREF="../Front/Contents.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Contents]" SRC="../Graphics/Contents.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Master.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Index]" SRC="../Graphics/Index.gif" ALIGN=Bottom></A><A REL=INDEX HREF="../Front/X_Symbol.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Symbols]" SRC="../Graphics/Symbols.gif" ALIGN=Bottom></A><A REL=GLOSSARY HREF="../Body/26_a.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Glossary]" SRC="../Graphics/Glossary.gif" ALIGN=Bottom></A><A HREF="../Front/X3J13Iss.htm"><IMG WIDTH=80 HEIGHT=40 ALT="[Issues]" SRC="../Graphics/Issues.gif" ALIGN=Bottom></A><BR>
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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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</BODY>
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</HTML>
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