You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
49 lines
1.3 KiB
C++
49 lines
1.3 KiB
C++
// future example
|
|
// adapted from http://www.cplusplus.com/reference/future/future/
|
|
|
|
#include <iostream> // std::cout
|
|
#include <future> // std::async, std::future
|
|
#include <chrono> // std::chrono::milliseconds
|
|
|
|
// a non-optimized way of checking for prime numbers.
|
|
bool is_prime(long int x) {
|
|
for (long int i = 2; i < x; ++i) {
|
|
if (x%i == 0) return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void explicitly_waiting() {
|
|
int p = 817504243;
|
|
|
|
// call function asynchronously:
|
|
std::future<bool> fut = std::async(std::launch::async, is_prime, p);
|
|
|
|
// do something while waiting for function to set future:
|
|
std::cout << "checking, please wait" << std::flush;
|
|
std::chrono::milliseconds span(500);
|
|
while (fut.wait_for(span) == std::future_status::timeout) {
|
|
std::cout << '.' << std::flush;
|
|
}
|
|
std::cout << std::endl;
|
|
|
|
bool x = fut.get(); // retrieve return value
|
|
std::cout << p << " " << (x?"is":"is not") << " prime." << std::endl;
|
|
}
|
|
|
|
void implicitly_waiting() {
|
|
long int p2 = 685102597328182763;
|
|
|
|
std::future<bool> fut = std::async(std::launch::async, is_prime, p2);
|
|
std::cout << "just getting the result, doing an implicit wait():";
|
|
std::cout << std::endl;
|
|
bool x = fut.get();
|
|
std::cout << p2 << " " << (x?"is":"is not") << " prime." << std::endl;
|
|
}
|
|
|
|
int main() {
|
|
explicitly_waiting();
|
|
implicitly_waiting();
|
|
return 0;
|
|
}
|