annotate 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
rev   line source
adamc@397 1 datatype list t = Nil | Cons of t * list t
adamc@397 2
adamc@501 3 fun length (t ::: Type) (ls : list t) =
adamc@501 4 let
adamc@501 5 fun length' (ls : list t) (acc : int) =
adamc@501 6 case ls of
adamc@501 7 Nil => acc
adamc@501 8 | Cons (_, ls') => length' ls' (acc + 1)
adamc@501 9 in
adamc@501 10 length' ls 0
adamc@501 11 end
adamc@397 12
adamc@501 13 fun rev (t ::: Type) (ls : list t) =
adamc@501 14 let
adamc@501 15 fun rev' (ls : list t) (acc : list t) =
adamc@501 16 case ls of
adamc@501 17 Nil => acc
adamc@501 18 | Cons (x, ls') => rev' ls' (Cons (x, acc))
adamc@501 19 in
adamc@501 20 rev' ls Nil
adamc@501 21 end