adamc@397: datatype list t = Nil | Cons of t * list t
adamc@397: 
adamc@823: fun length [t] (ls : list t) =
adamc@501:     let
adamc@501:         fun length' (ls : list t) (acc : int) =
adamc@501:             case ls of
adamc@501:                 Nil => acc
adamc@501:               | Cons (_, ls') => length' ls' (acc + 1)
adamc@501:     in
adamc@501:         length' ls 0
adamc@501:     end
adamc@397: 
adamc@823: fun rev [t] (ls : list t) = 
adamc@501:     let
adamc@501:         fun rev' (ls : list t) (acc : list t) =
adamc@501:             case ls of
adamc@501:                 Nil => acc
adamc@501:               | Cons (x, ls') => rev' ls' (Cons (x, acc))
adamc@501:     in
adamc@501:         rev' ls Nil
adamc@501:     end