error: expected constructor, destructor, or type conversion before & token

If you get the following error
"error: expected constructor, destructor, or type conversion before & token"
or
"error: expected initializer before & token"

Add "std::" before the token, if token is part of std namespace.
like std::ostream.
You can also think of adding "using namespace std;" in your source file but Please don't add using line in your header file.