Pairs

• In Haskell, you can construct a pair of values:

       (1, "foo")             :: (Int, String)

       (True, [])             :: (Bool, [a])

       (1, (True, "foo"))     :: (Int, (Bool, String))

• If you have values x :: a and y :: b you can construct:

         (x, y)     ::   (a, b)

• If you have value z :: (a,b), you can extract:

         fst z      ::   a
         snd z      ::   b