Interesting! The quote "sometimes, nom can be almost as fast as regex" has been removed from the Nom docs, so it's probably become faster since 2018 when that Cloudcity article was written. In fact, Nom now claims to "outperform many parser combinators library like Parsec and attoparsec, some regular expression engines and even handwritten C parsers" [1].

Someone used Nom for Advent of Code last year and found "The regex approach benchmarked at about 1ms while the parser approach benchmarked at 145 nanoseconds." [2] Maybe I'll try benchmarking Nom vs. regex for a follow-up post.

I find regexes are easier than parser combinators for simple tasks. If the problem is small, parser combinators are overkill. But if the problem gets complicated, I think parser combinators are more readable. You can break a parser combinator into small, well-documented, well-tested parts more easily than a big regex. But I still use regex more in my work, because most complex parsing I just throw into serde.

[1] https://github.com/Geal/nom

[2] https://www.christopherbiscardi.com/advent-of-code-2020-in-r...