!7

sclass Calculation {
  O f;
  OKOrError result;
  
  *() {}
  *(O *f) {}
  
  void calc() {
    try {
      result = OKOrError_ok(callF(f));
    } catch e {
      result = OKOrError_error(e);
    }
  }
}

p {
  Calculation c = new Calculation(f now);
  c.calc();
  print("Result: " + c.result);
  
  c = new Calculation(f fail);
  c.calc();
  print("Result: " + c.result);
}