auto Calculate = [](int ms, int num) {

std::this_thread::sleep_for(std::chrono::milliseconds(ms));

return num;

};

clock_t time = clock();

// Asynchronous.

std::future<int> f1 = std::async(Calculate, 10, 1);

std::future<int> f2 = std::async(Calculate, 20, 2);

std::future<int> f3 = std::async(Calculate, 30, 3);

// The get() blocks until the result is returned.

int sum = f1.get() + f2.get() + f3.get();

std::cout << "test_feture_time result is :" << sum

<< ", " << clock() - time << std::endl;

std::future<void> f1 = std::async(PrintChar, 'A');

std::future<void> f2 = std::async(PrintChar, 'B');

std::future<void> f3 = std::async(PrintChar, 'C');

for (int i = 0; i < 5; i++) {

std::cout << "D ";

}

f1.get(), f2.get(), f3.get();

std::cout << std::endl;

std::future<void> f1 = std::async(std::launch::async, PrintChar, 'A');

std::future<void> f2 = std::async(std::launch::async, PrintChar, 'B');

std::future<void> f3 = std::async(std::launch::async, PrintChar, 'C');

for (int i = 0; i < 5; i++) {

std::cout << "D ";

}

f1.get(), f2.get(), f3.get();

std::cout << std::endl;

std::future<void> f1 = std::async(std::launch::deferred, PrintChar, 'A');

std::future<void> f2 = std::async(std::launch::deferred, PrintChar, 'B');

std::future<void> f3 = std::async(std::launch::deferred, PrintChar, 'C');

for (int i = 0; i < 5; i++) {

std::cout << "D ";

}

// In std::launch::deferred.

// The new thread was not immediately started to execute

// when the std::async function was created.

// It only executes when get() is called.

f1.get(), f2.get(), f3.get();

std::cout << std::endl;

std::cout << "Test 1 : " << std::endl;

TestAsync1();

std::cout << "Test 2 <Default>: " << std::endl;

TestAsync2();

std::cout << "Test 3 <std::launch::async>: " << std::endl;

TestAsync3();

std::cout << "Test 4 <std::launch::deferred>: " << std::endl;

TestAsync4();

return 0;

}