What's wrong with this piece of code?

[xz]

It's just a comman operator<<

friend std::ostream& operator<<(std: :ostream& os, const Vertex& v){
return os << "(" << v.getX() << ", " << v.getY()<< ")";
};

The compiling error is:

Vertex.h: In function 'std::ostream& operator<<(std: :ostream&, const
Vertex
&)':
Vertex.h:39: error: no match for 'operator<<' in 'os << "("'


Am I missing some subtle mistake there?

[xz]

Re: What's wrong with this piece of code?

Oh, I figured it out.....