-- tail recursion through higher-order functions
module test017;

open import Stdlib.Prelude;

sumb : Nat → (Nat → Nat → Nat) → Nat → Nat;
sumb acc f zero := acc;
sumb acc f (suc x) := f acc x;

terminating
sum' : Nat → Nat → Nat;
sum' acc x := sumb (x + acc) sum' x;

sum : Nat → Nat;
sum := sum' 0;

main : IO;
main := printNatLn (sum 10000);

end;