Fix.Prop
This module defines a few common partial orders, each of which satisfies the signature PROPERTY. These include Booleans, options, and sets.
PROPERTY
module Boolean : sig ... end
The lattice of Booleans.
module Option (X : sig ... end) : sig ... end
The type _ option, equipped with the ordering None <= Some x. This ordering is not a lattice.
_ option
None <= Some x
module Set (X : sig ... end) : sig ... end
The lattice of sets. The ordering is set inclusion. Therefore, the empty set is the bottom element.