+++ Edward A Kmett [Oct 28 12 17:08 ]:
It might be worth hunting for similar low hanging fruit as well.
No doubt a similar approach would work for isLetter, isDigit, toUpper, toLower, etc. One thing puzzles me, though. Maybe someone here will have an explanation. I added a test case to my benchmark for isSpace *imported* from Data.Char. The imported isSpace benchmarks much faster (up to 5X) than the isSpace_DataChar, even though the latter has the same definition as the former. Wren Thronton noticed this too, and suggests (in http://community.haskell.org/~wren/bytestring-lexing/test/bench/BenchIsSpace...) that the difference "appears to be something special in how the base library was compiled," but I have no idea what that could be. John