Folks, I'm having no end of problems with operator<< and proto. In the beginning, operator << was overloaded for stream output and everything worked OK, then I added the left shift operator<< to the list of protoized operators in the grammar and everything broke. The strange thing is that: std::cout << a+b; correctly finds my stream out overload: template <class Exp> inline std::ostream& operator << (std::ostream& os, const big_number_exp<Exp>& r) But std::cout << a; no longer calls: template <class Backend> inline std::ostream& operator << (std::ostream& os, const big_number<Backend>& r) But calls the proto << operator instead. I'm at a complete loss to explain this, both of my overloads are in the same namespace as their respective types, and as far as I can see both should be preferred to the proto versions. Before I start tearing my hair out, anyone any ideas? Thanks, John.