(define succ
  x -> (1+ x))

(define prim
  0 x _ -> x
  n? x f? -> (funcall f? (1- n?) (prim (1- n?) x f?)))

(define tuple 
  x y -> [x y])

(define inl
  [x _] -> x)

(define inr
  [_ y] -> y)
