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Re: character objects & representation issues
- To: RWK at MIT-MC
- Subject: Re: character objects & representation issues
- From: Daniel L. Weinreb <DLW at MIT-AI>
- Date: Sat ,16 Aug 80 19:20:00 EDT
- Cc: LISP-FORUM at MIT-MC
Ah. I see. You mention to motivations for character objects; one
works fine in "my" proposal (the one I construed out of what I think
GLS is saying; I take no credit), but the other has problems.
First, you want character objects for debugging, so that when you see a
capital A you can tell that it is a capital A rather than a 101 octal.
With "my" proposal, you do indeed get this, so long as you do your
debugging in NIL rather than on the Lisp Machine. I don't think
anyone has objections to this.
Secondly, you want character objects to print differently. Presumably
a capital A prints as #/A, rather than as 101. This would not work in
"my" proposal. If you ran the portable FOOBAR on the LispM, and it
prints a data structure, and then you run FOOBAR in NIL and it reads it
back in, then character objects can get converted to fixnums. I don't
see any solution to this problem, other than to meekly suggest that
maybe it is just not a very common thing. Code that wants to print
character for human eyes can be made portable by going through a FORMAT
control option whenever printing character objects, rather than ever
using PRINT directly.