1 #include 
     
       2 using namespace std; 3  4  5  6  7  8 namespace all 9 {10     //inline作用为默认调用11     inline namespace V201712     {13         void fun(int num)14         {15             cout << "int" << "V2017" << endl;16         }17     }18     namespace V201819     {20         void fun(int num)21         {22             cout << "int" << "V2018" << endl;23         }24 25         void fun(double num)26         {27             cout << "double" << "V2018" << endl;28         }29     }30 }31 32 void main()33 {34     all::fun(1);35     all::V2018::fun(1);36     cin.get();37 }