Overloading operator<< as a friend to a template class

[CrimzonRJ]

Theoretically, how are you supposed to overload << as friend to a
template class?

I keep getting an 'unresolved extern symbol' error.

Is this even a smart thing to do?

 

[lw1a2]

Theoretically, how are you supposed to overload << as friend to a
template class?

I keep getting an 'unresolved extern symbol' error.

Is this even a smart thing to do?

example:

#include <iostream>
using namespace std;

template <class T>
class A;

template <class T>
ostream& operator<<(ostream& os, const A<T>& a);

template <class T>
class A
{
friend ostream& operator<< <T>(ostream& os, const A&);
public:
A(T i, T j):i(i), j(j){}
private:
T i;
T j;
};

template <class T>
ostream& operator<<(ostream& os, const A<T>& a)
{
os<<"( "<<a.i<<", "<<a.i<<" )";
return os;
}

int main()
{
A<int> a(1, 1);
cout<<a<<endl;
system("pause");
return 0;
}

 

[CrimzonRJ]

I am writing the program with Visual Studio 2005 and there is a catch22
involved:
The problem is that the export keyword is not supported therefore I am
forced to put the template Implementations in the header file(is this
correct?).

 

[lw1a2]

plaster your code

 

[Greg Comeau]

I am writing the program with Visual Studio 2005 and there is a catch22
involved:
The problem is that the export keyword is not supported therefore I am
forced to put the template Implementations in the header file(is this
correct?).

Right, but a quick skim shows lw1a2 gave a sample that you would
put in the header file. How is your code different?

You may also wanna have a look at:
http://www.comeaucomputing.com/techtalk/templates/#export