srecord ackermann_int_vstackComputable(int a, int b) implements VStack.Computable<Int> {
  public void step(VStack stack, O subComputationResult) {
    if (subComputationResult == null) {
      if (a == 0)
        stack.return(b+1);
      else if (b == 0) {
        a--;
        b = 1;
      } else
        stack.push(new ackermann_int_vstackComputable(a, b-1));
    } else {
      a--;
      b = subComputationResult/Int;
    }
  }
}