(module sum
  (fn sum
    (doc "rekursive Summe 0..=n")
    (type (fn-type (params (own (con Int))) (ret (own (con Int)))))
    (params n)
    (body (if (app eq n 0) 0 (app + n (app sum (app - n 1))))))
  (fn main
    (type (fn-type (params) (ret (own (con Unit))) (effects IO)))
    (params)
    (body (app print (app sum 10)))))