From Undecidability.Shared.Libs.PSL Require Import FinTypes.
Definition Cardinality (F: finType) := | elem F |.
(* * Dupfreeness *)
(* Proofs about dupfreeness *)

Lemma dupfree_countOne (X: eqType) (A: list X) : (forall x, count A x <= 1) -> dupfree A.