Re: [Haskell-cafe] Haskell, C and Matrix Multiplication

On Mon, 17 Jan 2011 07:45:04 +0000 Blake Rain wrote:

So, after drinking some coffee and having a smoke, I started the Haskell version:

[foldl (+) 0 $ zipWith (*) x y | x <- m1, y <- transpose m2]

I don't think this is correct; it's type is (Num a) => [[a]] -> [[a]] -> [a] rather than the expected (Num a) => [[a]] -> [[a]] -> [[a]] How about: mult m1 m2 = [[foldl (+) 0 $ zipWith (*) x y | y<-transpose m2] | x<-m1] Regarding performance: did you make sure you're forcing the evaluation of the result matrix? Regards, Pedro