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71 lines
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<H2>Issue CONDITION-ACCESSORS-SETFABLE Writeup</H2>
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<PRE><B>Issue:</B> <A HREF="iss074.htm">CONDITION-ACCESSORS-SETFABLE</A><P>
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<B>Forum:</B> Cleanup<P>
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<B>References:</B> Condition System, version 18<P>
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<B>Category:</B> CLARIFICATION<P>
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<B>Edit History:</B> Version 1, 1/3/90 by Kim A. Barrett<P>
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<P>
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<B>Problem Description:<P>
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</B> It is presently unspecified whether the accessor functions defined for the<P>
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various <A REL=DEFINITION HREF="../Body/07_ffb.htm#standard"><B>standard</B></A> condition classes may be used as places for <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A>.<P>
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<P>
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<B>Proposal (CONDITION-ACCESSORS-SETFABLE:NO):<P>
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</B> The effect of using accessor functions defined for the various <A REL=DEFINITION HREF="../Body/07_ffb.htm#standard"><B>standard</B></A><P>
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(i.e., pre-defined) condition classes as places for <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A> is undefined.<P>
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<P>
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<B>Rational:<P>
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</B> Conditions are used to record state at a particular point in time. Allowing<P>
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them to be modified at some later time makes little sense. The Condition<P>
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System does say that it is an error to attempt to assign a condition's slots<P>
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by using <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A>.<P>
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<P>
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<B>Current Practice:<P>
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</B> IIM does not make these functions be setfable.<P>
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<P>
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<B>Cost to Implementors:<P>
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</B> Implementations might want to change all the DEFINE-CONDITIONs to use<P>
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:READER rather than :ACCESSOR when defining the accessor methods on the<P>
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slots is fairly trivial--however technically this issue itself does not<P>
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force the need for that change. Fixing any code which currently depends<P>
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on being able to <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A> one of these accessors might be more work in some<P>
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implementations.<P>
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<P>
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<B>Cost to Users:<P>
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</B> Programs which currently depend on being able to <A REL=DEFINITION HREF="../Body/a_setf.htm#setf"><B>SETF</B></A> these accessors are<P>
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already non-portable.<P>
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<P>
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<B>Benifits:<P>
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</B> Users will know what to expect.<P>
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<P>
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<B>Discussion:<P>
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</B> Pitman and Barrett supports proposal NO.<P>
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</PRE>
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