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
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