\begin{ccRefClass}{Output_rep} \ccDefinition The purpose of \ccc{Output_rep} is to provide a way to control output formatting that works independently of the object's stream output operator. If you dont specialize \ccc{Output_rep} for \texttt{T}, \texttt{T}'s stream output operator is called from within \ccc{Output_rep}, by default. If you want another behaviour for your type \texttt{T}, you have to provide a specialization for that type. Furthermore, you can provide specializations with a second template parameter (a formatting tag). The second template parameter defaults to \ccc{Null_tag} and means \textsc{default behaviour}. Specializations of \ccc{Output_rep} should provide the following features: \begin{ccExampleCode} template< class F > struct Output_rep< Some_type, F > { Output_rep( const Some_type& t ); std::ostream& operator()( std::ostream& out ) const; }; \end{ccExampleCode} You can also specialize for a formatting tag \texttt{F}. \end{ccRefClass}