A() method, iterative version
  /** PARSE METHOD for A -> V { '+' V } **/

  Object A()
    {
    Object result;
    Object V1 = V();
    if( isFailure(V1) ) return failure;

    result = V1;

    while( skipWhitespace() && nextCharIs('+') )
      {
      Object V2 = V();
      if( isFailure(V2) ) return failure;
      result = OpenList.list("+", result, V2);
      }
    return result;
    }