Can parser combinators be made efficient?

Question

Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently rev

Answer 1

In a nutshell, parser combinators are slow for lexing.

There was a Haskell combinator library for building lexers (see "Lazy Lexing is Fast" Manuel M. T. Chakravarty) - as the tables were generated at runtime, there wasn't the hassle of code generation. The library got used a bit - it was initially used in one of the FFI preprocessors, but I don't think it ever got uploaded to Hackage, so maybe it was a little too inconvenient for regular use.

In the OCaml code above, the parser is directly matching on char-lists so it can be as fast as list destructuring is in the host language (it would be much faster than Parsec if it were re-implemented in Haskell). Christian Lindig had an OCaml library that had a set of parser combinators and a set of lexer combinators - the lexer combinators were certainly much simpler than Manuel Chakravarty's, and it might might be worthwhile tracking down this library and bench-marking it before writing a lexer generator.