Hi, I've been looking at the Haskell parser in ghc/compiler/GHC/Parser.y. It relies on post-processing pretty heavily, both to determine the type of parsed expressions (i.e. is "(x,y)" a pattern or expression?) and to reject invalid syntax (i.e. field declarations are parsed as a type, but this is rejected during postprocessing I think, except in constructor declarations). This makes the grammar rather hard to read. To quote [1]:
Insteadof describingthe languageto be parsed,thegrammardescribes theprocessused to parseit; it'smore like a hand-crafted parsing program,butcrammed into Backus-Naur Form. Does anybody know if there is another version of the parser generator uses grammar rules that are closer to the grammar rules in the 2010 report? Maybe a GLR grammar?
Also, I see that Happy is able to generate GLR parsers. I'm curious if GLR parsers aren't being used just because they are slow, or if there is some other reason they are hard to use. I am not an expert on parsing or grammars, so any insight would be appreciated. Thanks! -BenRI [1] https://escholarship.org/uc/item/8559j464