view demo/list.ur @ 2005:f3b0c82e2b13

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author Adam Chlipala <adam@chlipala.net>
date Sat, 26 Apr 2014 11:54:44 -0400
parents 669ac5e9a69e
children
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datatype list t = Nil | Cons of t * list t

fun length [t] (ls : list t) =
    let
        fun length' (ls : list t) (acc : int) =
            case ls of
                Nil => acc
              | Cons (_, ls') => length' ls' (acc + 1)
    in
        length' ls 0
    end

fun rev [t] (ls : list t) = 
    let
        fun rev' (ls : list t) (acc : list t) =
            case ls of
                Nil => acc
              | Cons (x, ls') => rev' ls' (Cons (x, acc))
    in
        rev' ls Nil
    end