On Sunday 04 February 2007 08:28, Stefan O'Rear wrote:
On Sun, Feb 04, 2007 at 08:20:23AM +0000, Dominic Steinitz wrote:
Someone suggested
pad :: Num a => [a] -> [a] pad = pad' 0 where pad' !l [] = [0x80] ++ ps ++ lb where pl = (64-(l+9)) `mod` 64 ps = replicate pl 0x00 lb = i2osp 8 (8*l) pad' !l (x:xs) = x : pad' (l+1) xs
but that didn't compile
*Main> :r [2 of 2] Compiling Main ( allInOne.hs, interpreted )
allInOne.hs:83:14: Parse error in pattern Failed, modules loaded: Codec.Utils.
Dominic.
The '!' is a GHC extension, enabled using the flag '-fbang-patterns'.
The test program runs to completion but still has a space leak consuming over 25m.
Equivalently, you can use Haskell 98's "seq" :
pad :: Num a => [a] -> [a] pad = pad' 0 where pad' l [] | l `seq` False = undefined pad' l [] = [0x80] ++ ps ++ lb where pl = (64-(l+9)) `mod` 64 ps = replicate pl 0x00 lb = i2osp 8 (8*l) pad' l (x:xs) = x : pad' (l+1) xs
The first alternative never succeeds, but to see that the compiler must force the evaluation of 'l'.
dom@heisenberg:~/sha1> ./allInOne 1000001 +RTS -hc -RTS [2845392438,1191608682,3124634993,2018558572,2630932637] [2224569924,473682542,3131984545,4182845925,3846598897] Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize' to increase it. Dominic. PS I appreciate all the help I'm getting.