std::deque<T,Allocator>::emplace_front (3) - Linux Man Pages
template< class... Args > (since C++11)
void emplace_front( Args&&... args ); (until C++17)
template< class... Args > (since C++17)
reference emplace_front( Args&&... args );
Inserts a new element to the beginning of the container. The element is constructed through std::allocator_traits::construct, which typically uses placement-new to construct the element in-place at the location provided by the container. The arguments args... are forwarded to the constructor as std::forward<Args>(args)....
All iterators, including the past-the-end iterator, are invalidated. No references are invalidated.
T (the container's element type) must meet the requirements of EmplaceConstructible.
(none) (until C++17)
A reference to the inserted element. (since C++17)
If an exception is thrown, this function has no effect (strong exception guarantee).
push_front (public member function)