On 2013-08-09 17:28, Frerich Raabe wrote:
On 2013-08-09 17:04, Joerg Fritsch wrote:for 0 <= i < row dimension of A for 0 <= j < column dimension of B for 0 <= k < column dimension of A = row dimension of B sum += (read A (i,k))* (read B(k,j))
[..]
-- This is one way to write your pseudo code in Haskell products :: Matrix -> Matrix -> Int products a b = sum $ do i <- [1..rows a] j <- [1..columns b] k <- [1..columns a] return $ readValue a (i, k) * readValue b (k, j)
It just occurred to me that the ranges of i, j and k are not quite correct, e.g. [1..rows a] should be [0..rows a - 1] to match your pseudo code. That aside, 'products' is probably not a very appropriate name. In any case, you could also keep your approach of building all 3-tuples and then map a function which turns the tuples into products over the list, like: products :: [(Int, Int, Int)] -> [Int] products = map (\i j k -> readA (i, j) * readB (k, j)) ...and then call 'sum' on that. This function actually deserves the name. :-) -- Frerich Raabe - ra...@froglogic.com www.froglogic.com - Multi-Platform GUI Testing _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
