🚀 go-pugleaf

Christopher Deli wrote:


>>As you have seen, there is a technical problem with having
>>an operator: the return type.
>>Are you sure you *must* implement an operator or will an
>>ordinary member function be sufficient?
>>If your assignment explicitely states an operator, then I
>>would suggest to ask your teacher, how he thinks this should
>>work (Hint: it is impossible, since operator+ has to return
>>an object, but for polymorphism you would need a pointer or
>>a reference).
>>
>>--
>>Karl Heinz Buchegger
>>kbuchegg@gascad.at
>>
>>
> 
> Can I create a member function which serves the same function as an operator

> (is it possible to write a = c + b?)?


No. Thats what operators are for.
Your problem is not the + syntax. Your problem is that this functions has
to return an object and this object has to be of a specific type.

  * Either define the return type to be a base class type

       class A
       {
          A virtual operator+( const A& Arg );
       };

       class B : public A
       {
          A virtual operator+( const A& Arg );
       };

    But this will not work. At the moment that class B's operator+
    returns the result, which would be of type B, it will be sliced
    into an A object (it will loose all its B information, just the A
    part remains).

  * Don't make them virtual

    class A
    {
      A operator+( const A& Arg );
    };

    class B : public A
    {
      B operator+( const B& Arg );
    };

    But since they are not virtual, polymorphism will not work.

  * Prepare base class A, that there will be overloads:

    class B;
    class A
    {
      A virtual operator+( const A& Arg );
      B virtual operator+( const B& Arg );
    };

    class B : public A
    {
      B virtual operator+( const B& Arg );
    };

    Ugly. Why should class A know, that someone is inheriting from it?

> I tried to make a friend operator
> aswell but the same things happened.. Isn't it possible to change the static
> type of my pointer by type casting or something so it could be enough with
> and operator in the subclass?


look up dynamic_cast.
It may help you in this case.

-- 
Karl Heinz Buchegger
kbuchegg@gascad.at