DEFMAXing of ()

[JONL at MIT-MC (Jon L White)]

    Date: 1 December 1980 04:06-EST
    From: Alan Bawden <ALAN at MIT-MC>
    Just because a macro expanded into NIL, there is no reason to believe
    that the calculation involved in computing that NIL was trivial.
    It is a bug if the cache scheme doesn't work for NIL.
In this scheme, inherited from Chuck Rich's and integreated into PSZ's,
there was general agreement amongst those users that a () returned by
such a macro was the bug -- the output of such a macro should always
appear in an EVAL context, so returning (QUOTE () )  or (PROGN () )
should always be correct.  I'm leary of having MACROMEMO do that 
conversion (as GSB suggested), but will certainly fix it so that a given
cell won't get infinitely "cache"'d.  Is there any comment on GSB's
proposal to have MACROMEMO do the fixup at runtime?