std::forward_list<T,Allocator>::emplace_after (3) - Linux Manuals
template< class... Args > (since C++11)
iterator emplace_after( const_iterator pos, Args&&... args );
Inserts a new element into a position after the specified position in the container. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments, as supplied to the function.
No iterators or references are invalidated.
pos - iterator after which the new element will be constructed
args - arguments to forward to the constructor of the element
iterator to the new element.
If an exception is thrown (e.g. by the constructor), the container is left unmodified, as if this function was never called (strong exception guarantee).
insert_after (public member function)