
Hello,
I'm still to Haskell, and after I read through
http://users.aber.ac.uk/afc/stricthaskell.html#seq
I thought, that these tow fragments after term rewriting are really
the same:
myLength :: [a] > Integer
myLength xs = len xs 0
where len [] l = l
len (x:xs) l = l `seq` len xs (l+1)
main = print $ myLength [1..10000000]
 vs.
myLength :: [a] > Integer
myLength xs = len xs 0
where len [] l = l
len (x:xs) l = len xs $! (l+1)
main = print $ myLength [1..10000000]
main = print $ myLength [1..10000000]
But the first expression evaluates more then twice as fast as the
second one. Tested on GHC 6.10.4 and Windows XP, dual core (for what
it's worth)
It's on http://moonpatio.com/fastcgi/hpaste.fcgi/view?id=5321#a5321
btw.
I can't see the difference, especially as $! is expressed in terms of
seq
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