下面一个例子程序,编译运行没有问题。
#include <thread>
#include <future>
#include <iostream>
void f(int* first,
int* last,
std::promise<int> accumulate_promise)
{
int sum = std::accumulate(first, last, 0);
accumulate_promise.set_value(sum); // Notify future
}
int main()
{
int numbers[] = { 1, 2, 3, 4, 5, 6 };
std::promise<int> accumulate_promise;
std::future<int> accumulate_future = accumulate_promise.get_future();
std::thread work_thread(f, begin(numbers), end(numbers),
std::move(accumulate_promise));
accumulate_future.wait(); // wait for result
std::cout << "result=" << accumulate_future.get() << "\n";
work_thread.join(); // wait for thread completion
}
但是假如本人把f函数改成模板的形式,如下:
template<typename Iterator>
void f(Iterator first,
Iterator last,
std::promise<int> accumulate_promise)
{
int sum = std::accumulate(first, last, 0);
accumulate_promise.set_value(sum); // Notify future
}
就会编译不过,说thread::thread构造函数找不到这样的重载。
error: no matching function for call to “std::thread::thread(<unresolved overloaded function type>, int*, int*, std::remove_reference<std::promise<int>&>::type)”
这个错误是什么含义? 本人的模板用法不对吗?
谢谢。
解决方案
40
需要显式指定:
#include <iostream>
#include <numeric>
#include <thread>
#include <future>
template<typename Iterator>
void f(Iterator first,
Iterator last,
std::promise<int> accumulate_promise)
{
int sum = std::accumulate(first, last, 0);
accumulate_promise.set_value(sum);
}
int main()
{
int numbers[] = { 1, 2, 3, 4, 5, 6 };
std::promise<int> accumulate_promise;
std::future<int> accumulate_future = accumulate_promise.get_future();
std::thread work_thread(f<int*>, std::begin(numbers), std::end(numbers),
std::move(accumulate_promise));
accumulate_future.wait(); // wait for result
std::cout << "result=" << accumulate_future.get() << "\n";
work_thread.join(); // wait for thread completion
return 0;
}