用Haskell计算矩阵

a :: Matrix
a = [[2.0, 3.0, 4.0],
     [5.0, 6.0, -1.0]]

b :: Matrix
b = [[1.0, 0.0],
     [1.0, 1.0],
     [0.0, -1.0]]

matrixProduct :: Matrix -> Matrix -> Matrix
matrixProduct m p = [[ scalarProduct r c | c <- column p] | r <- m]

scalarProduct :: Vector -> Vector -> Float
scalarProduct xs ys = sum [x*y | (x,y) <- zip xs ys]

column :: Matrix -> Matrix
column y = [ [z!!j | z <- y] | j <- [0 .. s] ]
    where
    s = length (head y) - 1