On Sat, Oct 1, 2016 at 8:34 PM, David Feuer
Instead of scanning first (in lexing) to find the end of the number and then scanning the string again to calculate the number, start to calculate once the first digit appears.
Ah, yes. bytestring-lexing does that (among numerous other things). It does save a second pass over the characters, but I'm not sure what proportion of the total slowdown of typical parser combinators is actually due to the second pass, as opposed to other problems with the typical "how hard can it be" lexers/parsers people knock out. Given the multitude of other problems (e.g., using Integer or other expensive types throughout the computation, not forcing things often enough to prevent thunks and stack depth, etc), I'm not sure it's legit to call it a "parser vs lexer" issue. -- Live well, ~wren