operator overloading

This is a discussion on operator overloading within the C++ Programming forums, part of the General Programming Boards category; //hello.. i need some help... //i want to overload the << and the >> operators.. //in my main i have ...

  1. #1
    Akira
    Guest

    operator overloading

    //hello.. i need some help...

    //i want to overload the << and the >> operators..

    //in my main i have something like this:

    IndexedList<string> list1;
    string s;

    cout << "Please enter the first list:" << endl;
    cin >> s;

    for(int i = s.length() ; i >0; i--) cin.putback(s.at(i-1));
    cin >> list1;
    cin >> s;

    cout << list1;

    //in my header i have something like this:

    template<class ItemType>
    std::istream& operator>> (std::istream& is, ItemType& item)
    {
    is >> item.data;
    return is;
    }

    template< class ItemType>
    std:stream& operator<< (std:stream& os, ItemType item)
    {
    os << item.data;
    return os;
    }

    //when i run it i get these errors:

    e:\project7\proj7\indexedlist.h(59) : error C2228: left of '.data' must have class/struct/union type
    E:\project7\proj7\proj7.cpp(62) : see reference to function template instantiation 'class std::basic_ostream<char,struct std::char_traits<char> > &__cdecl operator <<(class std::basic_ostream<char,struct std::char_traits<char> > &,char *)' b
    eing compiled
    e:\project7\proj7\indexedlist.h(52) : error C2679: binary '>>' : no operator defined which takes a right-hand operand of type '' (or there is no acceptable conversion)
    E:\project7\proj7\proj7.cpp(63) : see reference to function template instantiation 'class std::basic_istream<char,struct std::char_traits<char> > &__cdecl operator >>(class std::basic_istream<char,struct std::char_traits<char> > &,class std:
    :basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &)' being compiled
    e:\project7\proj7\indexedlist.h(52) : error C2039: 'data' : is not a member of 'IndexedList<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >'
    E:\project7\proj7\proj7.cpp(66) : see reference to function template instantiation 'class std::basic_istream<char,struct std::char_traits<char> > &__cdecl operator >>(class std::basic_istream<char,struct std::char_traits<char> > &,class Inde
    xedList<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > &)' being compiled
    e:\project7\proj7\indexedlist.h(59) : error C2039: 'data' : is not a member of 'IndexedList<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >'
    E:\project7\proj7\proj7.cpp(80) : see reference to function template instantiation 'class std::basic_ostream<char,struct std::char_traits<char> > &__cdecl operator <<(class std::basic_ostream<char,struct std::char_traits<char> > &,class Inde
    xedList<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >)' being compiled
    Error executing cl.exe.



    //whats the problem here?

    //thanks

    //Akira

  2. #2
    Registered User kitten's Avatar
    Join Date
    Aug 2001
    Posts
    109
    I'd say that you're trying to call your >>-operator with right hand data type that has no .data variable. Or then it isn't accessible (private, protected).
    Making error is human, but for messing things thoroughly it takes a computer

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