compose = \f g x : f (g x)

succ = y (\self :
  triage
    1
    t
    (triage
      (t (t t))
      (\_ tail : t t (self tail))
      t))

size = (\x :
  (y (\self x :
    compose succ
      (triage
        (\x : x)
        self
        (\x y : compose (self x) (self y))
        x)) x 0))

size size