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<H2>Issue MAKE-LOAD-FORM-SAVING-SLOTS Writeup</H2>
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<PRE><B>Issue:</B> <A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>MAKE-LOAD-FORM-SAVING-SLOTS</B></A><P>
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Reference: X3J13/92-102, dpANS 12.24<P>
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<A REL=DEFINITION HREF="../Body/f_mk_ld_.htm#make-load-form"><B>MAKE-LOAD-FORM</B></A>, p.7-51<P>
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<A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>MAKE-LOAD-FORM-SAVING-SLOTS</B></A>, p.7-56<P>
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X3J13/92-2102, Kevin Gallagher comment #2<P>
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X3J13/92-3104, Kim Barrett comment #4<P>
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X3J13/89-526, Issue <A HREF="iss215.htm">LOAD-OBJECTS</A> (Version 4)<P>
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X3J13/91-485, Issue <A HREF="iss320.htm">SLOT-VALUE-METACLASSES</A> (Version 7)<P>
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<B>Category:</B> CLARIFICATION/CHANGE<P>
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<B>Edit History:</B> Version 1, 1/5/93, Kim Barrett<P>
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Version 2, 1/5/93, Kim Barrett (fix current practice)<P>
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Version 3, 1/6/93, Kim Barrett<P>
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(description is operational, move possible operators to notes)<P>
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<B>Status:</B> Proposal NO-INITFORMS accepted, March 1993<P>
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<P>
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<B>Problem Description:<P>
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</B><P>
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The description of the function <A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>MAKE-LOAD-FORM-SAVING-SLOTS</B></A> is expressed in<P>
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terms of <A REL=DEFINITION HREF="../Body/f_mk_ins.htm#make-instance"><B>MAKE-INSTANCE</B></A>, <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A> of <A REL=DEFINITION HREF="../Body/f_slt_va.htm#slot-value"><B>SLOT-VALUE</B></A>, and <A REL=DEFINITION HREF="../Body/f_slt_ma.htm#slot-makunbound"><B>SLOT-MAKUNBOUND</B></A>, which is a<P>
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mistake on several counts.<P>
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<P>
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1. It could be interpreted as indicating that slot initialization forms are<P>
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to be executed, with the values of the slots then modified by <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A> of<P>
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<A REL=DEFINITION HREF="../Body/f_slt_va.htm#slot-value"><B>SLOT-VALUE</B></A> or <A REL=DEFINITION HREF="../Body/f_slt_ma.htm#slot-makunbound"><B>SLOT-MAKUNBOUND</B></A>. This is not in the spirit of the overall<P>
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proposal that introduced this operator, which talks about allocation via the<P>
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function <A REL=DEFINITION HREF="../Body/f_alloca.htm#allocate-instance"><B>ALLOCATE-INSTANCE</B></A>. MCL2.0 in fact used that interpretation, and then<P>
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received bug reports from users who expected initforms to not be executed.<P>
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<P>
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2. None of these operators are defined by this document as being applicable<P>
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when the metaclass <A REL=DEFINITION HREF="../Body/t_stu_cl.htm#structure-class"><B>STRUCTURE-CLASS</B></A> is involved. A sufficiently literal<P>
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reading could cause one to conclude that in fact this specification requires<P>
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such applicability, which the committee explicitly decided against.<P>
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<P>
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<B>Proposal (MAKE-LOAD-FORM-SAVING-SLOTS:NO-INITFORMS):<P>
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</B><P>
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1. Replace the first paragraph of the Description section of the dictionary<P>
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entry for <A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>MAKE-LOAD-FORM-SAVING-SLOTS</B></A> with<P>
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<P>
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Returns \term{forms} that, when \term{evaluated}, will construct an<P>
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\term{object} equivalent to \param{object}, without \term{executing}<P>
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\term{initialization forms}. The \term{slots} in the new \term{object}<P>
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that correspond to initialized \term{slots} in \param{object} are<P>
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initialized using the values from \param{object}. Uninitialized \term{slots}<P>
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in \param{object} are not initialized in the new \term{object}.<P>
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\funref{make-load-form-saving-slots} works for any \term{instance} of<P>
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\typeref{standard-object} or \typeref{structure-object}.<P>
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<P>
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2. Add the following to the Notes section for <A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>MAKE-LOAD-FORM-SAVING-SLOTS</B></A>.<P>
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<P>
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When the \term{object} is an \term{instance} of \typeref{standard-object},<P>
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\funref{make-load-form-saving-slots} could return a creation form that<P>
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\term{calls} \funref{allocate-instance} and an initialization form that<P>
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contains \term{calls} to \macref{setf} of \funref{slot-value} and<P>
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\funref{slot-makunbound}, though other \term{functions} of similar effect<P>
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might actually be used.<P>
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<P>
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<B>Editorial Impact:<P>
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</B><P>
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A small cut and paste job.<P>
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<P>
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<B>Rationale:<P>
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</B><P>
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Addresses the problem description.<P>
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<P>
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<B>Examples:<P>
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</B><P>
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(<A REL=DEFINITION HREF="../Body/m_defpar.htm#defvar"><B>defvar</B></A> *initform-executed-counter* 0)<P>
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(<A REL=DEFINITION HREF="../Body/m_defstr.htm#defstruct"><B>defstruct</B></A> foo<P>
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(slot-1 (<A REL=DEFINITION HREF="../Body/m_incf_.htm#incf"><B>incf</B></A> *initform-executed-counter*)))<P>
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(<A REL=DEFINITION HREF="../Body/m_defpar.htm#defvar"><B>defvar</B></A> *foo* (make-foo))<P>
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*initform-executed-counter* => 1<P>
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(<A REL=DEFINITION HREF="../Body/f_mapc_.htm#mapc"><B>mapc</B></A> #'<A REL=DEFINITION HREF="../Body/f_eval.htm#eval"><B>eval</B></A> (<A REL=DEFINITION HREF="../Body/m_mult_1.htm#multiple-value-list"><B>multiple-value-list</B></A> (<A REL=DEFINITION HREF="../Body/f_mk_l_1.htm#make-load-form-saving-slots"><B>make-load-form-saving-slots</B></A> *foo*)))<P>
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*initform-executed-counter* => 1<P>
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<P>
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<B>Current Practice:<P>
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</B><P>
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Apple Macintosh Common Lisp 2.0p2 implements this.<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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Probably small.<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 small. Only programs that were depending on the execution of<P>
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initforms would be negatively affected by this, and such programs are<P>
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probably already not portable.<P>
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<P>
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<B>Performance Impact:<P>
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</B><P>
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None.<P>
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<P>
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<B>Benefits:<P>
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</B><P>
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<B>Aesthetics:<P>
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</B><P>
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<B>Discussion:<P>
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</B><P>
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</PRE>
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