[full disclosure: I’m not a Menhir fanboi, b/c prefer LL(1). But I still recognize that it’s quite advanced and well-developed. Lots of stuff there that people don’t know commonly, but should.] After the thread about hand-written parsers, and the back-and-forth about LALR(1) parser-generators and…

I quite like the possibility to make rules that have parameters : this allows menhir to have a standard library, but you actually can make your own : option(X): | {None} | x=X{Some x} They can also be inlined

Yes its very nice ! Beside the quite obvious use cases that are given by the standard library, I have seen that feature used to add locations to anything this way : %public %inline located(X): x=X { Position.with_poss $startpos $endpos x } After that, in every rule you can use located(expr) if…

My two favourite features of Menhir, when compared to other parser generators, are checkpoints (or Incremental Interface), and the ability to marshal the intermediate representations (*.cmly files), that is the grammar and the automata. By the way Menhir is LR(1), not just LALR(1), so it can accept…

One of my favourite missing features from menhir is the ability to specify abstract precedence levels with a partial order between them, as provided by Dypgen ’s %relation keyword.

I came to like the incremental API and the declarative error reporting that you can use if you switch to the incremental API. However, merging and updating error description files is still a bit of a headache, even though it has improved, and I’m sure will keep improving.

My favorite feature is naturally the conflict explanation, which only requires the --explain flag to trigger (and should be the default mode, really). Here is for instance one of the conflicts you obtain if you forget to set the priority of INT higher than function application in an ML-ish language. …

I tend to prefer the explanations from Bison because they are less verbose and thus more readable. (Your mileage may vary.) But I agree with you that it is unfortunate that this is not the default behavior of this kind of tools. a.y: warning: shift/reduce conflict on token NAME [-Wcounterexamples] …

Where is your parser for Hack using menhir and this checkpoint-to-emulate-GLR thing?

You can find it here , freshly open-sourced thanks to help from @vsiles . The parser is based on your original Pfff php parser, the lexing hacks proved very useful. The “emulate GLR” stuff can be seen in the driver : it maintains a list of parsers, with some logic for backtracking and trying differen…

Your favorite Menhir tricks and fanciness

Ecosystem

Chet_Murthy February 17, 2021, 11:10pm 3

Menhir standard library! I never knew. Pages 17-18 of the manual, btw. Lovely!

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Your favorite Menhir tricks and fanciness

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