std::packaged_task<R(Args...)>::reset

void reset();

(since C++11)

Resets the state abandoning the results of previous executions. New shared state is constructed.

Equivalent to *this = packaged_task(std::move(f)), where f is the stored task.

Parameters

(none).

Return value

(none).

Exceptions

std::future_error if *this has no shared state. The error condition is set to no_state.
std::bad_alloc if there was not enough memory for a new shared state.
any exception thrown by the move constructor of the new packaged_task

Example

#include <iostream>
#include <cmath>
#include <thread>
#include <future>
 
int main()
{
    std::packaged_task<int(int,int)> task([](int a, int b) {
        return std::pow(a, b);
    });
    std::future<int> result = task.get_future();
    task(2, 9);
    std::cout << "2^9 = " << result.get() << '\n';
 
    task.reset();
    result = task.get_future();
    std::thread task_td(std::move(task), 2, 10);
    task_td.join();
    std::cout << "2^10 = " << result.get() << '\n';
}

Output:

2^9 = 512
2^10 = 1024

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