making ostream& operator<< a friend function of a class in a namespace

[Tim Partridge]

I want operator<< to be a friend function of a class inside a namespace, but
I don't know how. For example:

#include <iostream>

namespace ns {
class foo {
public:
// there is something wrong with the line below, but I don't
know how to fix it. I think I need to
// specify the namespace and class for the operator<<, but if I
write std:stream:perator<<
// i get all sorts of errors I don't understand.
friend std:stream& operator<<( std:stream &stream, const foo
&f );
private:
int i;
};
}

std:stream& operator<<( std:stream &stream, const ns::foo &f ) {
stream << f.i; // compiler complains i is private
return stream;
}

int main(int argc, char* argv[]) {
return 0;
}

 

[Sumit Rajan]

I want operator<< to be a friend function of a class inside a namespace, but
I don't know how. For example:

#include <iostream>

namespace ns {
class foo {
public:
// there is something wrong with the line below, but I don't
know how to fix it. I think I need to
// specify the namespace and class for the operator<<, but if I
write std:stream:perator<<
// i get all sorts of errors I don't understand.
friend std:stream& operator<<( std:stream &stream, const foo
&f );
private:
int i;
};
}

std:stream& operator<<( std:stream &stream, const ns::foo &f ) {
stream << f.i; // compiler complains i is private
return stream;
}

int main(int argc, char* argv[]) {
return 0;
}

#include <iostream>

namespace ns {
class foo {
public:
foo(int t=45):i(t){}
friend std:stream& operator<<( std:stream &stream, const
foo& f );
private:
int i;
};
std:stream& operator << ( std:stream &stream, const ns::foo &f );
// or you could define the operator right here
}

std:stream& ns:perator<<( std:stream &stream, const ns::foo &f ) {
stream << f.i;
return stream;
}

int main(int argc, char* argv[]) {
ns::foo f(4);
std::cout << f << '\n';
}