prog.cpp: In function 'std::shared_ptr<bool> f()':
prog.cpp:8:11: error: cannot convert 'std::deque<_Tp, _Alloc>::pop_front<int, std::allocator<int> >' from type 'void (std::deque<int>::)() noexcept' to type 'std::shared_ptr<bool>'
return q.pop_front;
^