How do you do generic programming in Haskell?

measure :: [a] -> Integer

measure [] = 0

measure (h:r) = 1 + measure r

GHCi, version 6.8.2: http://www.haskell.org/ghc/  :? for help
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Prelude> let swap (a,b) = (b,a)
Prelude> swap("hello", "world")
("world","hello")
Prelude> swap(1,2)
(2,1)
Prelude> swap("hello",2)
(2,"hello")