Einleitung

reverse [1,2,3,4] = [4,3,2,1]
reverse "foobar"  = "raboof"
reverse :: [a] -> [a]

reverse ist polymorph

sort [5,1,4,3] = [1,3,4,5]
sort "foobar"  = "abfoor"

sort :: [a] -> [a] -- ??
sort [sin,cos,log]  = ??

sort ist eingeschränkt polymorph