-- tail recursion through higher-order functions

function sumb((integer, integer) -> integer, integer, integer) : integer {
  push arg[1];
  push 0;
  eq;
  br {
    true: {
      push arg[2];
      ret;
    }
    false: {
      push arg[2];
      push 1;
      push arg[1];
      sub;
      push arg[0];
      tcall $ 2;
    }
  };
}

function sum'(integer, integer) : integer {
  push arg[1];
  push arg[0];
  add;
  push arg[0];
  calloc sum' 0;
  tcall sumb;
}

function sum(integer) : integer {
  push 0;
  push arg[0];
  tcall sum';
}

function main() {
  push 1000;
  tcall sum;
}