proposition: Theorem lelistA_dec : forall a xs, {lelistA leA a xs} + {~ lelistA leA a xs}.
proof: Proof. Proof with auto. destruct xs as [ | x xs ]... destruct (leA_dec a x)... right. intros J. inversion J... Defined.
imports: Coq.Lists.List Coq.Lists.SetoidList Metalib.CoqUniquenessTac