std::move()

 1 #include <iostream>
 2 #include <utility>
 3 #include <vector>
 4 #include <string>
 5 int main()
 6 {
 7     std::string str = "Hello";
 8     std::vector<std::string> v;
 9  
10     // uses the push_back(const T&) overload, which means
11     // we‘ll incur the cost of copying str
12     v.push_back(str);
13     std::cout << "After copy, str is \"" << str << "\"\n";
14  
15     // uses the rvalue reference push_back(T&&) overload,
16     // which means no strings will copied; instead, the contents
17     // of str will be moved into the vector.  This is less
18     // expensive, but also means str might now be empty.
19     v.push_back(std::move(str));
20     std::cout << "After move, str is \"" << str << "\"\n";
21  
22     std::cout << "The contents of the vector are \"" << v[0]
23                                          << "\", \"" << v[1] << "\"\n";
24 }