{

std::istringstream iss_numbers{"3 4 1 42 23 -23 93 2 -289 93"};

std::istringstream iss_letters{" a 23 b,e a2 k k?a;si,ksa c"};

std::vector<int> numbers;

std::vector<char> letters;

std::promise<void> numbers_promise, letters_promise;

auto numbers_ready = numbers_promise.get_future();

auto letter_ready = letters_promise.get_future();

std::thread value_reader([&]

{

// I/O operations.

std::copy(std::istream_iterator<int>{iss_numbers},

std::istream_iterator<int>{},

std::back_inserter(numbers));

//Notify for numbers.

numbers_promise.set_value();

std::copy_if(std::istreambuf_iterator<char>{iss_letters},

std::istreambuf_iterator<char>{},

std::back_inserter(letters),

::isalpha);

//Notify for letters.

letters_promise.set_value();

});

numbers_ready.wait();

std::sort(numbers.begin(), numbers.end());

if (letter_ready.wait_for(std::chrono::seconds(1)) ==

std::future_status::timeout)

{

//output the numbers while letters are being obtained.

for (int num : numbers) std::cout << num << ' ';

numbers.clear(); //Numbers were already printed.

}

letter_ready.wait();

std::sort(letters.begin(), letters.end());

//If numbers were already printed, it does nothing.

for (int num : numbers) std::cout << num << ' ';

std::cout << '\n';

for (char let : letters) std::cout << let << ' ';

std::cout << '\n';

value_reader.join();

return 0;