This file defines additional operations on native rb_maps and rb_sets.
These structures are defined in core in
They are meta objects, and are generally the most efficient dictionary structures
to use for pure metaprogramming right now.
of_list_core empty l turns a list of keys into an
It takes a user_provided
rb_set to use for the base case.
This can be used to pre-seed the set with additional elements,
and/or to use a custom comparison operator.