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Parser Combinators Beat Regexes

(entropicthoughts.com)
120 points mooreds | 1 comments | 09 Apr 25 21:53 UTC | HN request time: 0.203s | source
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yen223 ◴[10 Apr 25 00:49 UTC] No.43639551[source]▶
Parser combinators are one of those ideas that is really powerful in practice, but will never be mainstream because it had the bad fortune of coming from the functional programming world. It's a shame too, because parser combinators are what made parsers click for me.

Take the hard problem of parsing a language, break it down into the much simpler problem of reading tokens, then write simple "combinators" (and, or, one_or_many, etc etc) to combine these simple parsers into larger more complex parsers.

You could almost build an entire parser combinator library from scratch from memory, because none of the individual components are complicated.

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1. zahlman ◴[11 Apr 25 04:01 UTC] No.43650405[source]▶
> break it down into the much simpler problem of reading tokens, then write simple "combinators" (and, or, one_or_many, etc etc) to combine these simple parsers into larger more complex parsers.

The popular `pyparsing` library for Python (https://pypi.org/project/pyparsing/) expresses these concepts, just written more in traditional OO style rather than functional style (i.e. there are classes like OneOrMany that you instantiate, rather than binding a single-token-matcher argument to lambda or whatever).