adamc@397: datatype list t = Nil | Cons of t * list t
adamc@397: 
adamc@397: fun length' (t ::: Type) (ls : list t) (acc : int) =
adamc@397:     case ls of
adamc@397:         Nil => acc
adamc@397:       | Cons (_, ls') => length' ls' (acc + 1)
adamc@397: 
adamc@397: fun length (t ::: Type) (ls : list t) = length' ls 0
adamc@397: 
adamc@397: fun rev' (t ::: Type) (ls : list t) (acc : list t) =
adamc@397:     case ls of
adamc@397:         Nil => acc
adamc@397:       | Cons (x, ls') => rev' ls' (Cons (x, acc))
adamc@397: 
adamc@397: fun rev (t ::: Type) (ls : list t) = rev' ls Nil