[Haskell-cafe] Simple matrix

[Atila Romero]

I made a very simple matrix module that implements matrix sum and 
multiplication.

It does not require any especific type since it uses Num [[a]]. So 
instead of typing something like
Matrix [[1,0],[0,2]] * Matrix [[1,2],[3,4]]
you can just type
[[1,0],[0,2]]*[[1,2],[3,4]]

It needs -fglasgow-exts

Atila


module SimpleMatrix where

instance Num a => Num [[a]] where
  fromInteger x = [[fromInteger x]]
  abs x = map (map abs) x
  (+) [ ]  y  = y
  (+)  x  [ ] = x
  (+)  x   y  = zipWith (zipWith (+)) x y
  (*)  x   y  = map (matrixXvector x) y
    where
--    matrixXvector :: Num a => [[a]] -> [a] -> [[a]]
      matrixXvector m v = foldl vectorsum [] $ zipWith vectorXnumber m v
--    vectorXnumber :: Num a => [a] -> a -> [a]
      vectorXnumber v n = map (n*) v
--    vectorsum :: [a] -> [a] -> [a]
      vectorsum [] y = y
      vectorsum x [] = x
      vectorsum x  y = zipWith (+) x y


		
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