all tasks

Task/Vector-products/Haskell/vector-products.hs

@@ -0,0 +1,32 @@
+type Vector a = [a]
+type Scalar a = a
+
+a,b,c,d :: Vector Int
+a = [ 3,  4,  5 ]
+b = [ 4,  3,  5 ]
+c = [-5,-12,-13 ]
+d = [ 3,  4,  5,  6 ]
+
+dot :: (Num t) => Vector t -> Vector t -> Scalar t
+dot u v | length u == length v = sum $ zipWith (*) u v
+        | otherwise = error "Dotted Vectors must be of equal dimension."
+
+cross :: (Num t) => Vector t -> Vector t -> Vector t
+cross u v | length u == 3 && length v == 3 =
+             [u !! 1 * v !! 2 - u !! 2 * v !! 1,
+              u !! 2 * v !! 0 - u !! 0 * v !! 2,
+              u !! 0 * v !! 1 - u !! 1 * v !! 0]
+          | otherwise = error "Crossed Vectors must both be three dimensional."
+
+scalarTriple :: (Num t) => Vector t -> Vector t -> Vector t -> Scalar t
+scalarTriple q r s = dot q $ cross r s
+
+vectorTriple :: (Num t) => Vector t -> Vector t -> Vector t -> Vector t
+vectorTriple q r s = cross q $ cross r s
+
+main = do
+   mapM_ putStrLn [ "a . b     = " ++ (show $ dot a b)
+                  , "a x b     = " ++ (show $ cross a b)
+                  , "a . b x c = " ++ (show $ scalarTriple a b c)
+                  , "a x b x c = " ++ (show $ vectorTriple a b c)
+                  , "a . d     = " ++ (show $ dot a d) ]