CODEWITHSUNDEEP
c++operator-overloadingclass-template
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Reputation: 23

Passing an object as a parameter of an overloaded operator+ in a template class

I'm trying to pass an object as a parameter of an overloaded operator+ (and the class is a template class) but it's giving me an error which states:

error C2955: 'Kvader': use of class template requires template argument list

this is my class:

template <class Q>
class Kvader {
private:
    Q a, b, c;
public:
    Kvader(const Kvader &temp);
    Kvader operator+(Kvader);
};

and this is my overloaded+ method:

template <class Q>
Kvader Kvader<Q>::operator+(Kvader<int> temp) {
a += temp.a;
b += temp.b;
c += temp.c;
return *this;
}

I thought that 

Kvader Kvader<Q>::operator+(Kvader<int> temp)

would suffice as the argument list. What am I doing wrong?

In my main i'm just making 2 objects, (the second one calls the copy constructor) and then I try to add them together.

int main(){
Kvader<int> object1, object2(object1);
object1 = object1 + object2;

return 0;
}

Upvotes: 1

Views: 76

Answers (1)

iksemyonov
iksemyonov

Reputation: 4196

This code contains a few errors:

1) Kvader<Q> Kvader<Q>::operator+(Kvader<int> temp)

You need to specify the argument list for the return type as well.

2) Kvader<Q> operator+(Kvader<int>);

Same as 1) + change the argument type to Kvader<int> instead of the generic Kvader<Q>.

3) Kvader<Q>(const Kvader<Q> &temp);

Same as 1).

4) Specify a default constructor for Kvader<Q> else the creation statement in main() is going to fail.

5) Also, operator+(const T&) should return a reference to allow for operator chaining. It also typically takes a const reference to avoid unnecessary copying.

6) Finally, unless you have a particular reason for doing it the way you've done it, things like operator+(const Kvader<Q>&) should be defined in a generic fashion first, and then be specialized, when there is a need to do so. The way you've written it, operator+(cont Kvader<int>&) only works for those types where the Q type of the this object can be added to an int. What you probably wanted to achieve, was to enable a specialization of Kvader with any certain parameter to be added to Kvader's with the same exact parameter. Then, you can create specializations for specific Q types, such as int.

I suggest you actually read up on class and function templates! They can be confusing at times, indeed.

Complete code:

template <class Q>
class Kvader {
private:
    Q a, b, c;
public:
    Kvader() {}
    Kvader(const Kvader<Q> &temp);
    Kvader& operator+(const Kvader<Q>& temp);
};

template <class Q>
Kvader<Q>& Kvader<Q>::operator+(const Kvader<Q>& temp) {
a += temp.a;
b += temp.b;
c += temp.c;
return *this;
}

template<class Q>
Kvader<Q>::Kvader(const Kvader<Q> &temp)
{}

int main(){
Kvader<int> object1, object2(object1);
object1 = object1 + object2;

return 0;
}

Upvotes: 1

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