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<H2>Issue MACROEXPAND-HOOK-INITIAL-VALUE Writeup</H2>
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<PRE><B>Forum:</B> Public Review<P>
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<B>Issue:</B> <A HREF="iss234.htm">MACROEXPAND-HOOK-INITIAL-VALUE</A><P>
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<B>References:</B> Moon's public review comment #15<P>
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<A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A> (p. 3-78)<P>
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<B>Category:</B> CHANGE<P>
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<B>Edit history:</B> 21 Dec 1992, Version 1 by Loosemore<P>
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<B>Status:</B> Proposal IMPLEMENTATION-DEPENDENT passed 9-0-0, Mar 1993<P>
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<P>
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<P>
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<B>Problem description:<P>
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</B><P>
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Page 3-78 says the initial value of *macroexpand-hook* is "a<P>
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designator for the function funcall". I think the initial value should<P>
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be implementation dependent, because some implementations use<P>
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*macroexpand-hook* to <A REL=DEFINITION HREF="../Body/f_provid.htm#provide"><B>provide</B></A> information to their program development<P>
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environment on which macros are in use.<P>
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<P>
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<P>
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<B>Proposal (MACROEXPAND-HOOK-INITIAL-VALUE:IMPLEMENTATION-DEPENDENT):<P>
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</B><P>
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(1) Change the description of the initial value of <A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A><P>
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to say that it is a designator for a function that is equivalent to<P>
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the function <A REL=DEFINITION HREF="../Body/f_funcal.htm#funcall"><B>FUNCALL</B></A>, but which can have additional <P>
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implementation-dependent side-effects.<P>
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<P>
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(2) Add to the notes section of the dictionary entry for<P>
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<A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A> a statement that users who put their own function<P>
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into <A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A> should consider saving the previous hook and<P>
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calling it from their function.<P>
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<P>
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<P>
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<B>Rationale:<P>
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</B><P>
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Adopting this proposal would make <A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A> more useful.<P>
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<P>
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<P>
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<B>Current practice:<P>
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</B><P>
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Unknown.<P>
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<P>
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<P>
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<B>Cost to implementors:<P>
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</B><P>
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None.<P>
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<P>
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<P>
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<B>Cost to users:<P>
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</B><P>
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Probably little or none.<P>
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<P>
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<P>
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<B>Aesthetics:<P>
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</B><P>
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Neutral.<P>
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<P>
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<P>
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<B>Editorial impact:<P>
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</B><P>
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The change is confined to the dictionary entry for <A REL=DEFINITION HREF="../Body/v_mexp_h.htm#STmacroexpand-hookST"><B>*MACROEXPAND-HOOK*</B></A>.<P>
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<P>
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<P>
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<B>Discussion:<P>
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</B><P>
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<P>
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<P>
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<P>
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<P>
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<P>
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<P>
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</PRE>
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<HR>
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