Add example code

Code.hs

@@ -0,0 +1,41 @@
+module Code where
+
+data WeekDay = Monday
+             | Tuesday
+             | Thursday
+             | Wednsday
+             | Friday
+             | Saturday
+             | Sunday
+  deriving (Show)
+
+
+f :: Int -> Int -> Int
+f x 0 = 1
+f x y = x * f x (y - 1)
+
+mod2 :: Int -> Int
+mod2 x
+  | x - 2 == 0 = 0
+  | x - 2 < 0  = x
+  | otherwise  = mod2 (x - 2)
+
+week :: [WeekDay]
+week = [Monday, Tuesday, Thursday, Wednsday
+       , Friday, Saturday, Sunday]
+
+isMonday :: WeekDay -> Bool
+isMonday Monday = True
+isMonday x      = False
+
+data Tree = Leaf Char
+          | Node Tree Int Tree
+  deriving Show
+
+data MaybeInt = NoError Int
+              | Error String
+
+calcSomething :: Int -> MaybeInt
+calcSomething x
+  | x < 100   = NoError (x * 5)
+  | otherwise = Error "Int out of range!"