doldol packs multiple flaggable data in a Flag value,
and checks its flags by cheap operators.
In the current version, doldol will handle Enum e in a Foldable or List only.
doldol comes from Korean word 돌돌 which is a mimetic presenting roll up fabrics or something like flags.
EnumSet is a sound library but only works with List (ex. toEnum).
I also need List interface only. However, the next version of my simulation project needs to support Traversal class. Therefore, I keep developing this.
Of course, you can use EnumSet with fromList etc., but when you consider performance seriously, let think one more time.