# <utility>

**[<utility>](https://en.cppreference.com/w/cpp/header/utility)** provides miscellaneous utilities: `std::pair<T, U>` (a two-element tuple), `std::move` (enable move semantics), `std::forward` (perfect forwarding), `std::swap`, and `std::exchange`.

`std::pair` is the building block for map key-value pairs, and `std::move` / `std::forward` are essential for writing efficient generic code.

## Example

This example uses pair to store key-value data and demonstrates move semantics to avoid copying vectors.

```cpp
// compile: g++ -std=c++11 -o utilityexample utilityexample.cpp
// run: ./utilityexample
// description: pair and move semantics

#include <utility>
#include <iostream>
#include <vector>

int main() {
    std::pair<int, std::string> p{42, "answer"};
    std::cout << "pair: " << p.first << ", " << p.second << "\n";
    
    std::vector<int> v1{1, 2, 3};
    std::vector<int> v2 = std::move(v1);
    std::cout << "moved vector size: " << v2.size() << ", v1 size: " << v1.size() << "\n";
    
    return 0;
}
```