proposition: Lemma removeA_length_In {A eqA} {_ : @Symmetric A eqA} {_ : @Transitive A eqA} {dec} x ls (HD : NoDupA eqA ls) (Hin : InA eqA x ls) : S (List.length (@removeA A eqA dec x ls)) = List.length ls.
proof: Proof. etransitivity; [ | eapply removeA_length; assumption ]. edestruct InA_dec; [ reflexivity | tauto ]. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts