September 2017 Update

Task/Dot-product/Haskell/dot-product-1.hs

@@ -1,3 +1,4 @@
+dotp :: Num a => [a] -> [a] -> a
 dotp a b | length a == length b = sum (zipWith (*) a b)
          | otherwise = error "Vector sizes must match"
 

Task/Dot-product/Haskell/dot-product-2.hs

@@ -0,0 +1,15 @@
+dotp
+  :: Num a
+  => [a] -> [a] -> Maybe a
+dotp a b
+  | length a == length b = Just $ sum (zipWith (*) a b)
+  | otherwise = Nothing
+
+main :: IO ()
+main = mbPrint $ dotp [1, 3, -5] [4, -2, -1] -- prints 3
+
+mbPrint
+  :: Show a
+  => Maybe a -> IO ()
+mbPrint (Just x) = print x
+mbPrint n = print n