On 2013-08-09 17:04, Joerg Fritsch wrote:
I would need some help to get to a reasonable function involving the DB read, addition and multiplication.
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))
I started like this but then somehow lost the compass:
main = do
map my.read (map ((x,y) -> "matrixA:" ++ show row ++ ":" ++ show column) [ (i, j, k) | i <- [1..50], j <- [1..20], k <- [1..30] ])
You could treat lists as monads and write code which looks very much like your pseudo code, something like this -- A few dummy definitions to make 'products' typecheck. data Matrix = Matrix rows :: Matrix -> Int rows = undefined columns :: Matrix -> Int columns = undefined readValue :: Matrix -> (Int, Int) -> Int readValue = undefined -- 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) -- Frerich Raabe - raabe@froglogic.com www.froglogic.com - Multi-Platform GUI Testing