(module forma_1_factorial

  (fn fact_acc
    (doc "Tail-recursive factorial accumulator: fact_acc(n, acc) = n!*acc.")
    (type
      (fn-type
        (params (own (con Int)) (own (con Int)))
        (ret (own (con Int)))))
    (params n acc)
    (body
      (if (app eq n 0)
        acc
        (tail-app fact_acc (app - n 1) (app * acc n)))))

  (fn fact
    (doc "Factorial of a non-negative Int.")
    (type
      (fn-type
        (params (own (con Int)))
        (ret (own (con Int)))))
    (params n)
    (body (app fact_acc n 1)))

  (fn main
    (type (fn-type (params) (ret (own (con Unit))) (effects IO)))
    (params)
    (body
      (seq
        (app print (app fact 5))
        (app print (app fact 10))))))