# <future>

**[<future>](https://en.cppreference.com/w/cpp/header/future)** provides `std::future<T>` and `std::promise<T>` for passing values or exceptions between threads. `std::async` launches a function on a thread pool (or synchronously, depending on the policy) and returns a future that you wait on for the result.

It's the standard way to express "run this on another thread and get the result later."

## Example

This example launches an asynchronous task that sleeps and returns a value, then retrieves the result by calling `get()` on the future.

```cpp
// compile: g++ -std=c++11 -pthread -o futureexample futureexample.cpp
// run: ./futureexample
// description: async task with future

#include <future>
#include <iostream>
#include <thread>

int slow_computation() {
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
    return 42;
}

int main() {
    auto fut = std::async(std::launch::async, slow_computation);
    
    std::cout << "waiting for result...\n";
    int result = fut.get();
    std::cout << "got: " << result << "\n";
    
    return 0;
}
```