proposition: Fact undiscernable_spec x y : x ≡ y <-> ~ x ≢ y.
proof: Proof. split. + intros H1 H2; revert H2 H1; apply discernable_undiscernable. + intros H f. destruct (bool_dec (f x) (f y)); auto. destruct H; exists f; auto. Qed.
imports: List Bool Undecidability.Shared.Libs.DLW.Utils(utils_list finite fin_quotient fin_dec utils_decidable) Undecidability.FOL.TRAKHTENBROT(notations utils decidable)