Re: Proposal #3 for MacLISP characters...

[Kent M. Pitman <KMP at MIT-MC>]

I submit the following as a possible plan for Maclisp characters as it 
describes a useful functionality without extremely little overhead.

For Maclisp, we could even CONS a set of fixnums (values #o0 through #o177
which were unique from the ones normal read would give). (Mis)Features:

* #/A ... etc could return those. INCH could also return from that table.

* The printer could know about them -- or at least GRINDEF.

* CHARACTERP or whatever could obviously be trivially defined and would
  be useful for debugging. In compiled code, it would probably want to just
  be a FIXP test tho'.

* `Character' fixnums would not be EQ to `normal' fixnums (this was never
   previously guaranteed anyway) but the mathy operations would still work 
   on them. 

* CHAR-UPCASE or whatever you call it could return a `character' fixnum
  but if you did normal math (getting back a normal fixnum) you'd have an
  object which still worked ok for maclispy operations, but which OUCH could
  be made to complain about non `character' fixnums -- good for debugging 
  code to be later moved to less tolerant systems. (TYI would of course take
  either kind of fixnum.)

* FIXP would still return T, so CASEQ would not complain about using 
  characters. ... Some other code which wanted characters to not be FIXP
  would possibly lose -- I suspect such code would be in the minority
  and hope that most such code would still usefully accept fixnums. eg,
	(DEFUN FOO (X)
	  (COND ((CHARACTERP X) ...)
	        ((FIXP X) (FOO (CHARACTER X)))
		...))