[Haskell-cafe] GLR parser for Haskell?
jo at durchholz.org
Tue Apr 20 19:15:43 UTC 2021
Am 20.04.21 um 13:12 schrieb Sven Panne:
> * Does the GLR parser generator detect ambiguities and report them
> to the grammar writer?
That would be a solution to the decision problem.
It could try heuristics though, but I have no idea whether this
particular parser does.
To me, ambiguities (like the shift/reduce &
> reduce/reduce conflicts in LALR parsing) are a big red flag and a sign
> of a questionable language/grammar: Even if the generator/parser is able
> to figure things out correctly, humans have a much harder time.
Some conflicts indicate language design problems, others do not.
If you are after an algorithm that has less unnecessary conflicts, try
ILALR (Sönke Kannapinn's PdD thesis - well-written and easy to
understand if you can deal with German; see
; my own analysis, years ago, concluded that ILALR should have its
conflicts exactly where a human would have difficulties parsing, but I
never progressed to a proof of concept).
Note that ILALR does does not help with conflict resolution; a user
would likely have less unexpected conflicts, but the remaining ones
wouldn't be easier to solve than with LALR.
But I may be wrong. As I said, I never used anything like that in anger.
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