c++ - Define friend template method outside namespace -

i have code following basic structure:

namespace a{      template<class t,unsigned dim>     class cmytable{         ...             public:             template<class t,unsigned dim>             friend std::ostream& operator<<(std::ostream& s, const cmytable<t,dim>& vec);         }          };  } 

the initial problem operator<< outside namespace a.

i tried solution : how define friends in global namespace within c++ namespace?

namespace a{      template<class t,unsigned dim>     class cmytable; }  template<class t,unsigned dim> std::ostream& operator<<(std::ostream& s, const cmytable<t,dim>& vec);  namespace a{      template<class t,unsigned dim>     class cmytable{         ...             public:             template<class t,unsigned dim>             friend std::ostream& ::operator<<(std::ostream& s, const cmytable<t,dim>& vec);         }          };  }  template<class t,unsigned dim> std::ostream& operator<<(std::ostream& s, const cmytable<t,dim>& vec){ // [...] } 

i got error : error c2063: 'operator <<' : not function inside class declaration.

public: template<class t,unsigned dim> friend std::ostream& ::operator<<(std::ostream& s, const cmytable<t,dim>&  

does have ideas ?

thanks.

if ostream overload has friend (needs access protected members) define inline can use template arguments passed class.

namespace a{      template<class t,unsigned dim>     class cmytable{         ...         public:         // template<class t,unsigned dim>  // shadow otherwise         friend std::ostream& operator<<(std::ostream& s, const cmytable<t,dim>& vec) {         // [...]         }     }; } 

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otherwise remove declaration class , namesapce , define outside templated overload.

remember doesn't have friend if doesn't need access private or protected elements.

namespace a{    template<class t,unsigned dim>    class cmytable{     ...         public:     }; }    template<class t,unsigned dim> std::ostream& operator<<(std::ostream& s, const a::cmytable<t,dim>& vec){ // [...] } 

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the third option keep friend define inside namespace a

namespace a{      template<class t,unsigned dim>     class cmytable{         public:             int i;          template<class v,unsigned e>         friend std::ostream& operator<<(std::ostream& s, const cmytable<v,e>& vec);     };    }; // //  namespace a{      template<class t,unsigned dim>     std::ostream& operator<<(std::ostream& s, const cmytable<t,dim>& vec) {         s << vec.i;     }  }