81 lines
5.2 KiB
HTML
81 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 -->
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>CLHS: Function GET-SETF-EXPANSION</TITLE>
|
|
<LINK HREF="../Data/clhs.css" REL="stylesheet" TYPE="text/css" />
|
|
<META HTTP-EQUIV="Author" CONTENT="Kent M. Pitman">
|
|
<META HTTP-EQUIV="Organization" CONTENT="LispWorks Ltd.">
|
|
<LINK REL=TOP HREF="../Front/index.htm">
|
|
<LINK REL=COPYRIGHT HREF="../Front/Help.htm#Legal">
|
|
<LINK REL=DISCLAIMER HREF="../Front/Help.htm#Disclaimer">
|
|
<LINK REL=PREV HREF="m_defi_3.htm">
|
|
<LINK REL=UP HREF="c_data_a.htm">
|
|
<LINK REL=NEXT HREF="m_setf_.htm">
|
|
</HEAD>
|
|
<BODY>
|
|
<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_defi_3.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="m_setf_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
|
|
|
|
<HR>
|
|
|
|
<A NAME="get-setf-expansion"><I>Function</I> <B>GET-SETF-EXPANSION</B></A> <P>
|
|
<P>
|
|
<P><B>Syntax:</B><P>
|
|
<P>
|
|
|
|
<B>get-setf-expansion</B> <I>place <TT>&optional</TT> environment</I><P> => <I>vars, vals, store-vars, writer-form, reader-form</I><P>
|
|
<P>
|
|
<P><B>Arguments and Values:</B><P>
|
|
<P>
|
|
<I>place</I>---a <A REL=DEFINITION HREF="26_glo_p.htm#place"><I>place</I></A>. <P>
|
|
<I>environment</I>---an <A REL=DEFINITION HREF="26_glo_e.htm#environment"><I>environment</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
|
|
<I>vars, vals, store-vars, writer-form, reader-form</I>---a <A REL=DEFINITION HREF="26_glo_s.htm#setf_expansion"><I>setf expansion</I></A>. <P>
|
|
<P><B>Description:</B><P>
|
|
<P>
|
|
Determines five values constituting the <A REL=DEFINITION HREF="26_glo_s.htm#setf_expansion"><I>setf expansion</I></A> for <I>place</I> in <I>environment</I>; see <A REL=CHILD HREF="05_aab.htm">Section 5.1.1.2 (Setf Expansions)</A>. <P>
|
|
If <I>environment</I> is not supplied or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, the environment is the <A REL=DEFINITION HREF="26_glo_n.htm#null_lexical_environment"><I>null lexical environment</I></A>. <P>
|
|
<P><B>Examples:</B><P>
|
|
<P>
|
|
<PRE>
|
|
(get-setf-expansion 'x)
|
|
=> NIL, NIL, (#:G0001), (SETQ X #:G0001), X
|
|
</PRE>
|
|
</TT> <P>
|
|
|
|
<PRE>
|
|
;;; This macro is like POP
|
|
|
|
(defmacro xpop (place &environment env)
|
|
(multiple-value-bind (dummies vals new setter getter)
|
|
(get-setf-expansion place env)
|
|
`(let* (,@(mapcar #'list dummies vals) (,(car new) ,getter))
|
|
(if (cdr new) (error "Can't expand this."))
|
|
(prog1 (car ,(car new))
|
|
(setq ,(car new) (cdr ,(car new)))
|
|
,setter))))
|
|
|
|
(defsetf frob (x) (value)
|
|
`(setf (car ,x) ,value)) => FROB
|
|
;;; The following is an error; an error might be signaled at macro expansion time
|
|
(flet ((frob (x) (cdr x))) ;Invalid
|
|
(xpop (frob z)))
|
|
|
|
</PRE>
|
|
</TT> <P>
|
|
<P><B>Affected By:</B> None.
|
|
<P>
|
|
<P><B>Exceptional Situations:</B> None.
|
|
<P>
|
|
<P><B>See Also:</B><P>
|
|
<P>
|
|
<A REL=DEFINITION HREF="m_defset.htm#defsetf"><B>defsetf</B></A>, <A REL=DEFINITION HREF="m_defi_3.htm#define-setf-expander"><B>define-setf-expander</B></A>, <A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> <P>
|
|
<P><B>Notes:</B><P>
|
|
<P>
|
|
Any <A REL=DEFINITION HREF="26_glo_c.htm#compound_form"><I>compound form</I></A> is a valid <A REL=DEFINITION HREF="26_glo_p.htm#place"><I>place</I></A>, since any <A REL=DEFINITION HREF="26_glo_c.htm#compound_form"><I>compound form</I></A> whose <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operator</I></A> <I>f</I> has no <A REL=DEFINITION HREF="26_glo_s.htm#setf_expander"><I>setf expander</I></A> are expanded into a call to <TT>(setf </TT><I>f</I><TT>)</TT>. <P>
|
|
<P>
|
|
<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/iss185.htm">GET-SETF-METHOD-ENVIRONMENT:ADD-ARG</A><LI> <A REL=CHILD HREF="../Issues/iss308.htm">SETF-METHOD-VS-SETF-METHOD:RENAME-OLD-TERMS</A><P></UL><HR>
|
|
|
|
<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>
|
|
|
|
<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
|
|
</BODY>
|
|
</HTML>
|