2016 Update

Task/Matrix-multiplication/Haskell/matrix-multiplication-3.hs

@@ -0,0 +1,26 @@
+foldlZipWith::(a -> b -> c) -> (d -> c -> d) -> d -> [a] -> [b]  -> d
+foldlZipWith _ _ u [] _          = u
+foldlZipWith _ _ u _ []          = u
+foldlZipWith f g u (x:xs) (y:ys) = foldlZipWith f g (g u (f x y)) xs ys
+
+foldl1ZipWith::(a -> b -> c) -> (c -> c -> c) -> [a] -> [b] -> c
+foldl1ZipWith _ _ [] _          = error "First list is empty"
+foldl1ZipWith _ _ _ []          = error "Second list is empty"
+foldl1ZipWith f g (x:xs) (y:ys) = foldlZipWith f g (f x y) xs ys
+
+multAdd::(a -> b -> c) -> (c -> c -> c) -> [[a]] -> [[b]] -> [[c]]
+multAdd f g xs ys = map (\us -> foldl1ZipWith (\u vs -> map (f u) vs) (zipWith g) us ys) xs
+
+mult:: Num a => [[a]] -> [[a]] -> [[a]]
+mult xs ys = multAdd (*) (+) xs ys
+
+test a b = do
+  let c = mult a b
+  putStrLn "a ="
+  mapM_ print a
+  putStrLn "b ="
+  mapM_ print b
+  putStrLn "c = a * b = mult a b ="
+  mapM_ print c
+
+main = test [[1, 2],[3, 4]] [[-3, -8, 3],[-2,  1, 4]]