how to pass <std::function<void(int)>> paramater in c++

Question

i'm trying to perform a thread pool design pattern in c++, but i'm stuck on passing a task function parameter in order to push it inside a list here is my code

  std::list<std::function<void(int)>> work_queue; 

my push function

 void pushTask(std::function<void(int)> func , int a) 
{ 
std::unique_lock<std::mutex> lck(wq_mutex);
work_queue.push_back(std::function<void(int)>(func),a));
 }   

and here my main function with the task functin

void calcul(int a){
std::cout << a << "\n";
}

int main(){
ThreadPool th(10);
th.pushTask(std::bind(&calcule,4));
return 0;

}

i getting an error in this line

   work_queue.push_back(std::function<void(int)>(func),a));

can anyone identify the issue please ?

Answer 1

You doing that wrong.

std::list<std::function<void()>> work_queue; // you do not need int here

void pushTask(std::function<void()> func) // so here it is also obsolete
{ 
    std::unique_lock<std::mutex> lck(wq_mutex);
    work_queue.push_back(std::move(func));
}

// now this will be ok
th.pushTask(std::bind(&calcule,4));
// but since this is C++11 lambda is preferred 
th.pushTask([]() { calcule(4); } );