fact: Fixpoint dom (C : Type) (E : list (atom*C)) : atoms := match E with | nil => empty | (x, _) :: E' => add x (dom E') end.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.AssocList Metalib.MetatheoryAtom Metalib.LibTactics