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<TITLE>CLHS: Section 5.1.3</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="05_abi.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="05_a.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="05_b.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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5.1.3 Treatment of Other Macros Based on SETF</H2> <P>
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<P>
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For each of the ``read-modify-write'' <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operators</I></A> in the next figure, and for any additional <A REL=DEFINITION HREF="26_glo_m.htm#macro"><I>macros</I></A> defined by the <A REL=DEFINITION HREF="26_glo_p.htm#programmer"><I>programmer</I></A> using <A REL=DEFINITION HREF="m_defi_2.htm#define-modify-macro"><B>define-modify-macro</B></A>, an exception is made to the normal rule of left-to-right evaluation of arguments. Evaluation of <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A> occurs in left-to-right order, with the exception that for the <I>place</I> <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A>, the actual <A REL=DEFINITION HREF="26_glo_r.htm#read"><I>read</I></A> of the ``old value'' from that <I>place</I> happens after all of the <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>argument</I></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> <A REL=DEFINITION HREF="26_glo_e.htm#evaluation"><I>evaluations</I></A>, and just before a ``new value'' is computed and <I>written</I> back into the <I>place</I>. <P>
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Specifically, each of these <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operators</I></A> can be viewed as involving a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> with the following general syntax: <P>
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<PRE>
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(<A REL=DEFINITION HREF="26_glo_o.htm#operator">operator</A> preceding-form* place following-form*)
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</PRE>
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</TT> <P>
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The evaluation of each such <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> proceeds like this: <P>
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<P><DL><DT>1. <A REL=DEFINITION HREF="26_glo_e.htm#evaluate"><I>Evaluate</I></A> each of the <I>preceding-forms</I>, in left-to-right order. <DD><DT>2. <A REL=DEFINITION HREF="26_glo_e.htm#evaluate"><I>Evaluate</I></A> the <A REL=DEFINITION HREF="26_glo_s.htm#subform"><I>subforms</I></A> of the <I>place</I>, in the order specified by the second value of the <A REL=DEFINITION HREF="26_glo_s.htm#setf_expansion"><I>setf expansion</I></A> for that <I>place</I>. <DD><DT>3. <A REL=DEFINITION HREF="26_glo_e.htm#evaluate"><I>Evaluate</I></A> each of the <I>following-forms</I>, in left-to-right order. <DD><DT>4. <A REL=DEFINITION HREF="26_glo_r.htm#read"><I>Read</I></A> the old value from <I>place</I>. <DD><DT>5. Compute the new value. <DD><DT>6. Store the new value into <I>place</I>. <P><DD></DL><P>
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<PRE>
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<A REL=DEFINITION HREF="m_incf_.htm#decf">decf</A> <A REL=DEFINITION HREF="m_pop.htm#pop">pop</A> <A REL=DEFINITION HREF="m_pshnew.htm#pushnew">pushnew</A>
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<A REL=DEFINITION HREF="m_incf_.htm#incf">incf</A> <A REL=DEFINITION HREF="m_push.htm#push">push</A> <A REL=DEFINITION HREF="m_remf.htm#remf">remf</A>
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</PRE>
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<P><B>Figure 5-9. Read-Modify-Write Macros</B> <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/iss287.htm">READ-MODIFY-WRITE-EVALUATION-ORDER:DELAYED-ACCESS-STORES</A><P></UL><HR>
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