cppreference.com > C++ Strings > empty empty Syntax:
      #include <string>
      bool empty() const;
The empty() function returns true if the string has no elements, false otherwise. For example, the following code uses empty() as the stopping condition on a (C/C++ Keywords) while loop to clear a string and display its contents in reverse order:
     vector<int> v;
     for( int i = 0; i < 5; i++ ) {
       v.push_back(i);
     }
     while( !v.empty() ) {
       cout << v.back() << endl;
       v.pop_back();
     }
Related topics: size