Comments (3)
Thanks for your input. That would indeed be useful. It would be much easier to create nice (e.g. clang-style) error messages if that information was available.
The Earley library doesn't know enough about the input token type to tell where new lines start and end, so it's not able to construct a Loc
on its own as it is. For that to work it would have to always work on Char
or L tokentype
(which is what you're doing). Though both seem useful, it is needlessly restrictive to commit to using only one of those.
Can we can find a way of doing it that does not sacrifice generality?
For what it's worth, your current approach seems good. It allows you to put location information in subexpressions, which you couldn't do with the proposed change to the library. You may also be able to get the information that you want by looking at the location of the first token in the unconsumed
field of the Report
(though the report is about how far it was able to parse before failing and not where individual parses were obtained).
from earley.
I realized this morning that my original proposal makes no sense, as you point out (the parser has no source information). I think all I need are some simple combinators, which might not even belong in Earley
itself:
locSymbol :: Eq t => t -> Prod r e (L t) (L t)
locSymbol = symbol . L NoLoc
locSatisfy :: (t -> Bool) -> Prod r e (L t) (L t)
locSatisfy p = satisfy (p . unLoc)
This works because the Eq
instance of L
ignores its Loc
from earley.
That looks like a nice approach. I'll close this issue now, but if you do come up with a better way to do it, we can revisit it.
from earley.
Related Issues (20)
- Q: How to do error recovery? HOT 1
- Wrong(?) result on some grammars with infinite results HOT 10
- Is Earley’s implementation related to Marpa? HOT 3
- Add a `eof` terminal HOT 5
- Behavior of Semigroup/Monoid instances for Prod? HOT 5
- Capture result as well as matched tokens HOT 2
- Generate ABNF/EBNF from Earley grammar HOT 1
- Suggestion: Make it so that `<$` rules return at most one result. HOT 3
- Parsing into a list delimited by a token HOT 5
- INDENT and DEDENT HOT 5
- feature: constraint validation of production parse result HOT 7
- Please add tags "test ambiguity" etc HOT 2
- Crashes if grammar is infinitely ambiguous on given input HOT 11
- Is it okey to use "many" and heavily use Applicative parsing techniques? HOT 2
- Diverges with sepEndBy from parser-combinator HOT 1
- Report doesn't include enough information HOT 2
- Is there any possible optimization for getting non-exhaustive outputs for ambiguous grammars HOT 1
- Disambiguate/Filter productions HOT 1
- Missing case for Constraint for fmap and <*> HOT 3
- Something like Ruby Slippers parsing HOT 1
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