Wiederholung Listen

Bezeichnungen bisher:

data List a  = Nil | Cons a (List a)
     Nil  :: List a
     Cons :: a -> List a -> List a

in Haskell-Prelude schon vordefiniert:

data     [a] = []  |      a : [a]

Anwendung:

import Prelude hiding ( length )
length :: [a] -> Int
length l = case l of
    []     -> 0
    x : xs -> 1 + length xs