text: #include <string>
  #include <string_view>
  
  int main() {
      std::string greeting = "Hello";
      std::string to       = "World";
  
      std::string msg = greeting + ", " + to;
      // msg is a new string of "Hello, World"
      
      std::string_view view(msg);
      // create a "view" into the string
  
      view.substr(0, 5);
      // returns new string_view of "Hello"
  
      view.substr(7);
      // returns new string_view of "World!"
  }
  