use int.Int
use int.MinMax
use bintree.Tree
use bintree.Height

let unTree (t: tree 'a)
    (onNode (x: 'a) (l r: tree 'a) { t = Node l x r })
    (onLeaf { t = Empty })
  = any

let rec height_cps (t: tree 'a) {} (ret (r:int) { r = height t })
= unTree {t}
    (fun (x: 'a) (l r: tree 'a) ->
        height_cps {l} (fun (hl:int) ->
        height_cps {r} (fun (hr:int) ->
        ret {1 + max hl hr})))
    (-> ret {0})