Am Sonntag, 16. Dezember 2007 04:07 schrieb Don Stewart:
------------------------------------------------------------------------ Program 7:
============================== hs/space-xxxxx-foldl.hs: {-# LANGUAGE BangPatterns #-}
cnt :: String -> Int cnt bs = foldl (\sum c -> if c == ' ' then sum+1 else sum) 0 bs
main = do s <- getContents print (cnt s)
Hmm. Lazy accumulator eh, on String? Should exhibit a space leak.
Doesn't (with -O2, at least), seems ghc's strictness analyser did a good job. It is indeed about 10* slower than ByteStrings, but very memory friendly - and, actually on my machine it's faster (not much) than Data.List.foldl' . And, again on my machine, Programme 3 is almost as slow when compiled with 6.8.1 and twice as slow when compiled with 6.6.1.
Nice little benchmark.
-- Don
Cheers, Daniel