On Friday 08 February 2002 22:14, you wrote: > define > > test1 l = > let s1 = foldr (+) 1 l > s2 = foldr (-) 1 l > in (s1, s2) > > test2 l = > let s = foldr (\x (a,b) -> (x+a,x-b)) (1,1) l > in s > > why is test1 so much faster than test2 for long lists l (eg > [1..1000000])? replacing foldr with foldl makes it faster (of course), > but test2 is still much slower. > > i *expected* test2 to be much faster because you're only traversing the > list once. presumably the two elements "a" and "b" in test2 could be put > in registers and i'd imagine test2 should be faster (it certainly would be > if written in c).
I'd say that's because in the second case you also got to apply the (,), besides the (+)/(-) constructor during the transversing... Am I right? J.A. _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
