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std::jthread::joinable(3)      C++ Standard Libary     std::jthread::joinable(3)

NAME
     std::jthread::joinable - std::jthread::joinable

Synopsis
	[[nodiscard]] bool joinable() const noexcept;  (since C++20)

	Checks	if the std::jthread object identifies an active thread of execu-
     tion.
	Specifically, returns true if get_id() != std::jthread::id(). So  a  de-
     fault
	constructed jthread is not joinable.

	A  thread  that has finished executing code, but has not yet been joined
     is still
	considered an active thread of execution and is therefore joinable.

Parameters
	(none)

Return value
	true if the jthread object identifies an  active  thread  of  execution,
     false
	otherwise.

Example
     // Run this code

      #include <chrono>
      #include <iostream>
      #include <thread>
      using namespace std::chrono_literals;

      void foo()
      {
	  std::this_thread::sleep_for(500ms);
      }

      int main()
      {
	  std::cout << std::boolalpha;

	  std::jthread t;
	  std::cout << "before starting, joinable: " << t.joinable() << '\n';

	  t = std::jthread{foo};
	  std::cout << "after starting, joinable: " << t.joinable() << '\n';

	  t.join();
	  std::cout << "after joining, joinable: " << t.joinable() << '\n';

	  t = std::jthread{foo};
	  t.detach();
	  std::cout << "after detaching, joinable: " << t.joinable() << '\n';

      }

Output:
      before starting, joinable: false
      after starting, joinable: true
      after joining, joinable: false
      after detaching, joinable: false

References
	  * C++23 standard (ISO/IEC 14882:2023):

	  * 33.4.4.3 Members [thread.jthread.mem]
	  * C++20 standard (ISO/IEC 14882:2020):

	  * 32.4.3.2 Members [thread.jthread.mem]

See also
	get_id returns the id of the thread
	       (public member function)
	join   waits for the thread to finish its execution
	       (public member function)
	detach	permits the thread to execute independently from the thread han-
     dle
	       (public member function)

http://cppreference.com 	   2024.06.10	       std::jthread::joinable(3)
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