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Reading the Readtable
- To: DLW at MIT-MC
- Subject: Reading the Readtable
- From: Alan Bawden <ALAN at MIT-MC>
- Date: Sat ,9 Jan 82 18:02:00 EDT
- Cc: BUG-LISPM at MIT-MC, Henry at MIT-AI
Date: Saturday, 9 January 1982, 14:20-EST
From: Daniel L. Weinreb <dlw at MIT-AI>
One problem with the existing feature is that there is no way to ask a
readtable what is in it. I admit that I don't know why you would want
this, but you might.
I know that this is a "problem" with the existing "feature". To be
able to return ssomething from (STATUS SYNTAX ...) that is USEFUL
(i.e. you can save the number someplace and then us it later in a
DIFFERENT readtable) is IMPOSSIBLE in general without re-implementing
the reader from the ground up and re-introducing various magic
meaningful "syntax bits" ala MacLisp. I repeat what I said before:
"There is NOTHING MEANINGFUL I could return from (STATUS SYNTAX ...)"
Also, Alan said:
I agree that having a symbolic name for a usefull syntax is a good
idea, but I cannot possibly think up names for all of them. Remember
that A is different from E is different from S etc. Do you have a
specific syntax that you think deserves a name?
in reply to Henry's:
Ideally, it would returns keywords as acceptable to
So maybe Henry is just asking for something that returns the "description"
without returning that information which differs between A and S.
I don't think I understand at all what it is that you think you are
asking for here. If I am allowed to ignore the difference between "A"
and "S", then how about the difference between "A" and "(", can I
ignore that too? Why don't I just always return NIL then? Do you
(get-syntax-description #/A) => ALPHABETIC
(get-syntax-description #/S) => ALPHABETIC
?? What happens if you were actually interested in the fact that "S"
can be used in small flonums? How am I supposed to decide this? What
about the difference between "+" and "-", do we judge that to be
I'd also be interested in knowing what the application is, though; maybe
there's a better solution that we should be implementing.
Thats what I said. Before we get off on flaming about all kind of
difficult/impossible ideas that I get to implement in my spare time,
why don't we find out what the application is. Not for a "better
solution", but for a "POSSIBLE solution".