(** Whether a list is sorted is a decidable proposition. *)
Section DecidableSorting.
Variable A : Type.
Variable leA : relation A.
Hypothesis leA_dec : forall x y, {leA x y} + {~ leA x y}.

(* Specifications: *)
Theorem lelistA_dec : forall a xs,
{lelistA leA a xs} + {~ lelistA leA a xs}.