Then how about a solution like this: I took your program but used my fast fileIterate instead of ,,foldl over getContents''. I also added {-# OPTIONS -funbox-strict-fields #-}, and played a bit to get the best optimisations from GHC.
It's about 7 times faster this way, but it's still two times slower than the solution I sent to shootout.
Devilish plan: Maybe we could have some variants of fileIterate in GHC's libraries? ;->
Two responses:
1. I agree that providing the right kind of library functions (and material explaining how to use them) maybe a key to getting efficient code without losing high-level forms of expression.
2. Your fileIterator certainly looks nicer (to me) than your other solution, but...
Tagging along with this debate, I found myself wondering if, in order to get performance comparable to other languages, it is really necessary to write code like code in other languages. E.g., I thought one of the lessons of John Hughes' "Why functional Programming matters" was that one can achieve greater efficiencies by climbing higher rather than dropping down to the level of other languages. Your fileIterate looks to me like a step in the right direction.
But I did wonder if it wouldn't be possible to also abstract out the I/O element of your 'fileIterate', using instead something like:
streamIterate :: [b] -> (a -> b -> a) -> a -> IO a
(I was originally thinking of something like:
streamIterate :: (c -> (b,c)) -> c -> (a -> b -> a) -> a -> IO a
where the first argument is a function that takes a sequence generator and returns the next member of the sequence+new generator, and the 2nd arg is the initial generator.)
For such an approach to be useful, I think it would also be important to have variations of functions like length, lines, words that can be combined to make a function like your wc'.
#g
------------ Graham Klyne For email: http://www.ninebynine.org/#Contact
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