Is there already a list class?

Did anything ever come of this discussion? http://www.haskell.org/pipermail/libraries/2007-January/006704.html I found myself writing this the other day to capture the fact that IA5 characters are the building blocks of IA5 strings. Dominic. newtype IA5String = IA5String {unIA5String :: String} newtype IA5Char = IA5Char {unIA5Char :: Char} class List a b | a -> b where nil :: b cons :: a -> b -> b instance List IA5Char IA5String where nil = IA5String [] cons x y = IA5String ((unIA5Char x):(unIA5String y))