c++ - passing template args to std::thread -

im having little problem passing args std::thread calls template function.

template <typename f, typename... a> void start(int interval, f func, a&&... args) {     if (_running.load(std::memory_order_acquire)) {         stop();     };     _running.store(true, std::memory_order_release);     _thread = std::thread([this, interval, func, args]()     {         while (_running.load(std::memory_order_acquire))         {             func(std::forward<a>(args)...);              (int = 0; (i <= (interval / 200)) && _running.load(std::memory_order_acquire); i++)                 std::this_thread::sleep_for(std::chrono::milliseconds(200));         }     }); } 

edit: added little more detail should able pass function "start" ammount or args

void threadproc(hwnd hwnd) {     beep(1000, 100); }  start(2000, threadproc, hwnd); 

error:

error c3520: 'args': parameter pack must expanded in context     note: see reference function template instantiation 'void callback::start<void(__cdecl *)(hwnd),hwnd&>(int,f,hwnd &)' being compiled     1>              1>          [     1>              f=void (__cdecl *)(hwnd)     1>          ] 

_thread = std::thread([this, interval, func, &args...]()