lab05: impl

lab05/maybeEither.hs

@@ -0,0 +1,25 @@
+getMax :: [Int] -> Maybe Int
+getMax [] = Nothing
+getMax x = Just (maximum x)
+
+reciprocal :: (Eq a, Fractional a) => a -> Maybe a
+reciprocal 0 = Nothing
+reciprocal x = Just (1/x)
+
+rectangleArea :: Int -> Int -> Either String Int
+rectangleArea x y
+  | x < 0 = Left "Width is not positive"
+  | y < 0 = Left "Height is not positive"
+  | otherwise = Right (x * y)
+
+main :: IO ()
+main = do
+  print $ getMax []
+  print $ getMax [99,12,37]
+  print $ getMax [-99,-12,-37]
+  print $ reciprocal 4
+  print $ reciprocal 2
+  print $ reciprocal 0
+  print $ rectangleArea 5 10
+  print $ rectangleArea (-5) 10
+  print $ rectangleArea 5 (-10)