# <functional>

**[<functional>](https://en.cppreference.com/w/cpp/header/functional)** provides function wrappers and factories: `std::function<Sig>` (type-erased callable), `std::bind` (partial application), and `std::mem_fn` (convert member function pointers to function objects). It also includes standard comparators and arithmetic function objects.

`std::function` is useful when you need to store or pass callables of different types; otherwise prefer lambdas or function pointers.

## Example

This example uses `std::function` as a generic callback holder that accepts different callable types (lambdas, function pointers).

```cpp
// compile: g++ -std=c++11 -o functionalexample functionalexample.cpp
// run: ./functionalexample
// description: std::function as a generic callback holder

#include <functional>
#include <iostream>

void execute(std::function<int(int)> f, int x) {
    std::cout << "result: " << f(x) << "\n";
}

int main() {
    auto lambda = [](int x) { return x * 2; };
    execute(lambda, 5);
    
    auto regular = [](int x) { return x + 10; };
    execute(regular, 5);
    
    return 0;
}
```