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Re: Reductions during Bison error handling
From: |
Richard Stallman |
Subject: |
Re: Reductions during Bison error handling |
Date: |
Tue, 21 May 2002 13:12:37 -0600 (MDT) |
I agree with this as a general principle. However, in this particular
case, Bison does not agree with its documentation. If we keep the
current behavior, we really ought to document it.
Yes, or at least we should try.
Given how difficult
LALR(1) parser internal behavior is to understand, I find it a little
unlikely that there can be any significant reliance on the obscure
places where current behavior differs from that documented.
This sort of thing happens all the time with undocumented features in
(say) Windows. People use trial and error and get something that works.
We certainly must not assume nobody depends on this merely because
it isn't documented.
There are other possible reasons which could be persuasive if they are
applicable. For instance, if the current behavior is to fail where it
ought to succeed, it is unlikely anyone would depend on that because
it is unlikely to be of use for any real task. If it reports an
error but at the wrong place, that can't be useful.
Can you,
in fact, describe the current behavior in Bison-user-level terms?
No, but that proves nothing--I have forgotten all these details.
Under the circumstances, I would be inclined instead to have a command
`%olderror' or `%traditionalerror' (or `%brokenerror' (:->)) to go in
the other direction.
IF it is possible for existing programs to depend on the current
behavior, that is too risky. If we can be sure no existing programs
depend on the current behavior, we don't need to support both modes.
- Re: Reductions during Bison error handling, (continued)
Re: Reductions during Bison error handling, Akim Demaille, 2002/05/20
- Re: Reductions during Bison error handling, Richard Stallman, 2002/05/20
- Re: Reductions during Bison error handling, Paul Hilfinger, 2002/05/20
- Re: Reductions during Bison error handling,
Richard Stallman <=
- Re: Reductions during Bison error handling, Hans Aberg, 2002/05/21
- Re: Reductions during Bison error handling, Richard Stallman, 2002/05/23
- Re: Reductions during Bison error handling, Akim Demaille, 2002/05/24
- Re: Reductions during Bison error handling, Hans Aberg, 2002/05/24
Re: Reductions during Bison error handling, Paul Eggert, 2002/05/21
Re: Reductions during Bison error handling, Paul Hilfinger, 2002/05/21
Re: Reductions during Bison error handling, Paul Eggert, 2002/05/22
Re: Reductions during Bison error handling, Paul Hilfinger, 2002/05/22
Re: Reductions during Bison error handling, Akim Demaille, 2002/05/23
Re: Reductions during Bison error handling, Hans Aberg, 2002/05/23