proposition: Lemma disjoint_one_l : forall A B (x : atom) (a : A) (E : list (asn A B)), disjoint (one (VarAsn B x a)) E <-> x `notin` dom E.
proof: Proof. intros. unfold disjoint; simpl_asnlist; split; fsetdec. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics