c++ - doubts regarding usage of :: (scope_resolution_operator) -
    when studying book on c++, came across this. if declare class,   class student {public: void func(int v1,int v2) {    //some code } //some members. };   and use function same name out of class (non-member function) like,   void func(int x,inty)   and if wish call non-member function in member function of above declared class, syntax be,   //inside member function... ::func(x,y); }   correct me if wrong.otherwise,  assuming wrote   using namespace std;   in beginning of program, below code equivalent previous one?   //inside member function std::func(x,y); }   and, answer change if use different namespace other std?? ie, provided use,   using namespace abc   are following declarations   abc::func(x,y)   and,   ::func(x,y)   absolutely equivalent under conditions or change under specific conditions??   thank you.             in beginning of program, below code equivalent previous one?   //inside member function   std::func(x,y);    no isn't. because preform qualified  name lookup...