Overload operator << for a template-nested private class

[renoraines]

I get this error:

error C2785: 'std::ostream &operator <<(std::ostream &,const Outsider<T>::Nested &)' and '<Unknown>' have different return types

When trying to compile the following code with VS2008:

#include <iostream>

using namespace std;

template <class T>
class Outsider {
	private:
		class Nested {
			private:
				T myData;
			public:
				Nested(const T &);
				friend ostream & operator << <>(ostream &, const Nested &);
		};
		Nested *myNested;
	public:
		Outsider(const T &);
		~Outsider();
		friend ostream & operator << <>(ostream &, const Outsider &);
};

template <class T>
Outsider<T>::Nested::Nested(const T &data) : myData(data) {}

template <class T>
ostream & operator << <>(ostream &out, const typename Outsider<T>::Nested &nested) {
	return out << data << endl;
}

template <class T>
Outsider<T>::Outsider(const T &data) : myNested(new Nested(data)) {}

template <class T>
Outsider<T>::~Outsider() {
	delete myNested;
}

template <class T>
ostream & operator << <>(ostream &out, const Outsider<T> &outsider) {
	return out << *outsider.myNested << endl;
}

void main() {
	Outsider<int> outsider(5);
	cout << outsider << endl;
}

Operator << compiles cleanly for the Outsider class but not for the Nested class. Why is this? How can I fix it?

Thanks

[R0mai]

More experencied programmers will correct me, but template definitions and declarations must be at the same place.

Also:
main() returns an int;
This is totally your decision but I think it's a bad practice that the
ostream & operator <<(ostream &, const someOtherClass&)
flushes the stream, and inserts a new line with <<std::endl.

So this is what I made from your code, this prints "5".

#include <iostream>

using namespace std;

template <class T>
class Outsider {
	private:
		class Nested {
			private:
				T myData;
			public:
				Nested(const T &data): myData(data) {}
				friend ostream & operator << (ostream &out, const Nested &nested) {
					return out << nested.myData << endl;
				}
		};
		Nested *myNested;
	public:
		Outsider(const T &data) : myNested(new Nested(data)) {}
		~Outsider() {
			delete myNested;
		}
		friend ostream & operator << (ostream &out, const Outsider &outsider) {
			return out << *outsider.myNested << endl;
		}
};

int main() {
	Outsider<int> outsider(5);
	cout << outsider << endl;
}

R0mai

[jsmith]

The problem is an extra <> in OP's operator<< declarations. Note they are missing in the response, which is the correct way to declare them.

[renoraines]

Thanks to both for the responses.

@R0mai:

I don't want to make the functions inline, can you post a code the compiles with function definitions outside of the class?

@jsmith:

I tried removing the <> in the declarations as well as the definitions and I still can't compile.

If I remove all <> (both in declarations and in definitions) I get an unresolved external symbol linker error for the operator << of Outsider.

If I leave the <> just in the definitions I get the same error.

And if I leave the <> just in the declarations or I use it both in declarations and in definitions, I get the original error:

error C2785: 'std::ostream &operator <<(std::ostream &,const Outsider<T>::Nested &)' and '<Unknown>' have different return types

[jsmith]

Just move the implementations of the operator<< into the class at the point of declaration.