What's wrong with this piece of code?

[xz]

It's just a comman operator<<

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

The compiling error is:

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


Am I missing some subtle mistake there?

 

[xz]

Oh, I figured it out.....