Preface_stdlib.EquivalenceImplementation for Equivalence.t.
An Equivalence is just a function that takes to 'a and return a bool.
module Contravariant : Preface_specs.CONTRAVARIANT with type 'a t = 'a tmodule Divisible : Preface_specs.DIVISIBLE with type 'a t = 'a tmodule Decidable : Preface_specs.DECIDABLE with type 'a t = 'a tmodule Invariant : Preface_specs.INVARIANT with type 'a t = 'a tAdditional functions to facilitate practical work with Equivalence.t.