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Parser Combinators Beat Regexes

(entropicthoughts.com)
120 points mooreds | 3 comments | 09 Apr 25 21:53 UTC | HN request time: 0s | source
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DadBase ◴[10 Apr 25 01:55 UTC] No.43639894[source]▶
Parser combinators are great until you need to parse something real, like CSV with embedded newlines and Excel quotes. That’s when you reach for the reliable trio: awk, duct tape, and prayer.
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1. masklinn ◴[10 Apr 25 05:32 UTC] No.43640949[source]▶
Seems like exactly the situation where you’d want parsers, because they can do any form of quoting \ escaping you want and have no reason to care about newlines any more than they do any other character.
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2. DadBase ◴[10 Apr 25 14:11 UTC] No.43643957[source]▶
Parsers can handle it, sure, but then you blink and you're ten layers deep trying to explain why a single unmatched quote ate the rest of the file. Sometimes a little awk and a strong coffee gets you further.
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3. maxbond ◴[10 Apr 25 23:22 UTC] No.43648879[source]▶
Use what's working for you but one of the strengths of parser combinators is managing abstraction so that you can reason locally rather than having to manage things "ten layers deep." That's more of a problem in imperative approaches where you are manually managing a complex state machine, and can indeed have very deep `if` hierarchies.

Parser combinator are good at letting you express the grammar as a relationship among functions so that the compiler handles the nitty-gritty and error prone bits. (Regexes also abstract away these details, of course.)