Issue: SETF-SUB-METHODS (Version 4)

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

The writeup is much improved.  I favor SETF-SUB-METHODS:DELAYED-ACCESS-STORES.

I don't think it's accurate to say there is no cost to users.  For
example, the original setf of getf example, which was proposed by a
user, will behave differently under this proposal than it behaved in
several implementations.  Users of those implementations might have been
depending on the old behavior.  You can say there is no effect on
portable programs, but you can't say that no users will be affected.
Even users who had ported programs among several implementations
and mistakenly concluded that their programs were portable might
be affected.

I think the <dont care>s in the test cases should be removed.  CLtL
specifies specific values to be returned by all these forms; while 
those values are irrelevant to the current issue, I think it is
better practice to include them in the test cases.  Otherwise
someone might think you were proposing to stop specifying specific
values to be returned, and allow the values to become
implementation-dependent.

I was asked to provide Current Practice information for Symbolics:

Symbolics Genera 7.2 foolishly adopted an earlier proposal
(SETF-METHOD-FOR-SYMBOLS) before it was officially approved by X3J13 and
its parent standards organization.  This proposal is incompatible with
that one, so Genera 7.2 does not implement the behavior described here,
and fails test cases 1, 2, 4, 5, and 6.  I believe Symbolics Genera 7.1
is closer to this proposal, however I don't have access to it so I didn't
test it.

I didn't test Symbolics CLOE, perhaps Kent can provide information on it.

An earlier version of the proposal had Current Practice information
for Xerox, Franz, HP, and DEC.  Where did it go?