view demo/list.ur @ 758:8323c1beef2e

Subforms type-checks; lists urlified and unurlified
author Adam Chlipala <adamc@hcoop.net>
date Thu, 30 Apr 2009 11:48:56 -0400
parents 7ef4b2911b09
children 669ac5e9a69e
line wrap: on
line source
datatype list t = Nil | Cons of t * list t

fun length (t ::: Type) (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 ::: Type) (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