add a map and set example with custom data type as key

mapSet.hs

@@ -0,0 +1,39 @@
+import qualified Data.Map as Map
+import qualified Data.Set as Set
+import Data.Set ((\\))
+
+data CustomKey = Foo | Bar | Baz
+  deriving (Show, Eq, Ord)
+
+main = do
+    putStrLn "basic map behaviour: "
+    let m = Map.fromList [("k1", 7), ("k2", 13)]
+    putStrLn ("map: " ++ show m)
+    putStrLn ("v1: " ++ show (Map.lookup "k1" m))
+    putStrLn ("size: " ++ show (Map.size m))
+
+    let m' = Map.delete "k2" m
+    putStrLn ("map after delete v2: " ++ show m')
+    putStrLn ("v2: " ++ show (Map.lookup "k2" m'))
+
+    putStrLn "using a custom data type as a Key in a map:"
+    let m1 = Map.fromList [(Foo, "Hello"), (Baz, "Goodbye")]
+    putStrLn ("map with custom key type: " ++ show m1)
+    putStrLn ("v1: " ++ show (Map.lookup Foo m1))
+
+    let m1' = Map.insert Bar "How do you do?" m1
+    putStrLn ("map after insert: " ++ show m1')
+
+    let s = Set.fromList [7, 13]
+    putStrLn ("set: " ++ show s)
+    putStrLn ("is 7 a member? "++ show (Set.member 7 s) )
+    putStrLn ("size: " ++ show (Set.size s))
+
+    let s' = Set.fromList [7, 11, 12, 18, 13, 42]
+    putStrLn ("second set: " ++ show s')
+    putStrLn ("union: " ++ (show (s `Set.union` s')))
+    putStrLn ("difference: "++ (show (Set.difference s' s)))
+    putStrLn ("isSubset: " ++ (show (Set.isSubsetOf s s')))
+
+    let s1 = Set.insert 1 s'
+    putStrLn ("set after insert:" ++ show s1)