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From: Gregor@parc.xerox.com (Gregor Kiczales)
Newsgroups: comp.lang.clos
Subject: Re: Creating metaclasses
Message-ID: <91May2.094725pdt.29186@tracer-bullet.parc.xerox.com>
Date: 2 May 91 16:47:14 GMT
References: <9105020636.AA28415@kuwait>
Sender: welch@tut.cis.ohio-state.edu
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Its great that the Lucid implementations supports this, and it would be
great if other implementations did as well.  But, the excerpt quoted by
Richard Harris does, in fact, have the effect of not requiring
implementations to support this.

The reason for this restriction is that optimizations are easier if the
implementor can be assured that the entire meta-level program has been
defined before any of the base-level program is instantiated.  This
makes it possible to compute any optimizations at the time the
base-level program is instantiated.  Furthermore, since the meta-level
program isn't permitted to change, it isn't necessary to be able to
update those optimizations.