std::deque<T,Allocator>::pop_front
From cppreference.com
                    
                                        
                    
                    
                                                            
                    
|   void pop_front();  | 
||
Removes the first element of the container. If there are no elements in the container, the behavior is undefined.
| Iterators and references to the erased element are invalidated. It is unspecified whether the past-the-end iterator is invalidated if the element is the last element in the container. Other references and iterators are not affected. | (until C++11) | 
| Iterators and references to the erased element are invalidated. If the element is the last element in the container, the past-the-end iterator is also invalidated. Other references and iterators are not affected. | (since C++11) | 
Parameters
(none)
Return value
(none)
Complexity
Constant.
Exceptions
Does not throw.
See also
|    removes the last element   (public member function)  | |
|    inserts an element to the beginning  (public member function)  |