void push_front(const T &x)
Push an element x into the vector from front.
These functions come from std::list and std::deque, and have identical behaviors to their counterparts in std::list/stddeque.
http://www.cplusplus.com/reference/stl/deque/pop_front.html http://www.cplusplus.com/reference/stl/deque/push_front.html