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    std::hash<std::thread::id>

    From cppreference.com
     
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    Defined in header <thread>
    template<> struct hash<std::thread::id>;
    		 (since C++11)
    See More

    The template specialization of std::hash for the std::thread::id class allows users to obtain hashes of the identifiers of threads.

    Example

    This section is incomplete
    Reason: example that uses hash meaningfully
    Run this code
    #include <chrono>
#include <iostream>
#include <thread>
#include <vector>
using namespace std::chrono_literals;

void foo()
{
    std::this_thread::sleep_for(10ms);
}
 
int main()
{
    std::vector<std::thread> v;
    for (int n = 0; n < 4; ++n)
        v.emplace_back(foo);

    std::hash<std::thread::id> hasher;
    for (auto& t : v)
    {
        std::cout << "thread " << t.get_id() << " hashes to "
                  << hasher(t.get_id()) << '\n';
        t.join();
    }
}

    Possible output: 

    thread 139786440144640 hashes to 8905351942358389397
thread 139786431751936 hashes to 9222844670065909738
thread 139786423359232 hashes to 18199000599186780501
thread 139786414966528 hashes to 15386662774029264672

    See also

    (C++11)
    		 hash function object
    (class template) [edit]