[erlang-questions] Better error messages would be helpful

Sun May 19 01:41:32 CEST 2013

> On May 17, 2013, at 9:40 AM, David Mercer <dmercer@REDACTED> wrote:
>> Richard A. O'Keefe wrote:
>>> Part of the problem is precisely the fact that the parser is written in
>>> Yecc.
>> Back in the day, I'd have known the answer to this, but I figure some of
>> you are more knowledgeable than I ever was: What parsing technology
>> besides hand-rolled would produce better error messages?  ANTLR?
>> Parsec?  PEG?
> Menhir
> http://gallium.inria.fr/~fpottier/menhir/

Menhir is definitely interesting, and if I had experienced anything
other than extreme frustration with Godi, I would have liked to
try it.  But judging from section 8 of the Menhir manual, a
Menhir-built parser would be no better than a Yecc-built one here.
It might even be worse: the manual says that the current lookahead
token is *replaced* by an ERROR token as part of recovery, and in
the example we are discussing, the token in question is ")" and it
is correct, and should be retained.  What is more, the Menhir manual
is quite explicit that error detection may be deferred.

What the user needs in cases like this is the information that
an earlier token (fun) caused the parser to be looking for a
particular token (end) but it encountered a closer (right paren)
before finding it.  Something basically top-down should have an
easier time of it.

More information about the erlang-questions mailing list