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From: Gregor@parc.xerox.com (Gregor Kiczales)
Newsgroups: comp.lang.clos
Subject: Re: Controlling the class of effective-slot-definition objects
Message-ID: <91May8.125743pdt.29186@tracer-bullet.parc.xerox.com>
Date: 8 May 91 19:57:33 GMT
References: <9105032201.AA13370@cs.rpi.edu>
Sender: welch@tut.cis.ohio-state.edu
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Organization: CommonLoops
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   Date: 	Fri, 3 May 1991 15:01:41 PDT
   Xns-Originator: george@cis.ohio-state.EDU
   From: harrisr@cs.rpi.edu (Richard Harris)

   I want to control the class of my effective-slot-definitions
   based in information in my direct-slot-definitions, but the MOP
   is so vague on how compute-effective-slot-definition computes
   the initargs argument to effective-slot-definition-class that
   I can't figure out how to do this.

I agree that it is difficult to tell how this works from the MOP
document.  One can only imagine just what the people who wrote it were
thinking :-)

One possibility is to continue to use PCL, as you are doing.  The other
is to retrofit the PCL behavior into the existing protocol.  In other
words, define a method on COMPUTE-EFFECTIVE-SLOT-DEFINITION which itself
calls COMPUTE-EFFECTIVE-SLOT-DEFINITION-INITARGS and follows that
protocol.  You should be able to define a default method on
COMP---INITARGS using a dummy class metaobject class to generate dummy
calls to effective-slotd-class.

Note that vendors could, as a compatible extension to the documented
protocol, introduce COMP---INITARGS themselves.