An interface for a type with a binary, associative operator over it and a privileged unit value.
A Monoid is a Semigroup enriched an identity element, called unit.
Some well known monoids are
type t = intop = (+)unit = 0type t = intop = ( * )unit = 1type t = stringop = (^)unit = ""module type Seed = sig ... endmodule type S = sig ... endA monoid is a set of objects with an associative binary operation over it and a privileged unit element that acts as an identity.
Law notes the laws that should be obeyed by any instantiation of Monoid in the form of predicates that should hold true for any arguments of the appropriate type.
Module functors for creating implementations of Monoid
make (unit : t) (op : t -> t -> t) is an implementation of Monoid over the type t with the given unit and op
val of_semigroup :
(module Semigroup.S with type t = 'a) ->
'a ->
(module S
with type t = 'a)of_semigroup semi unit forms an implementation of Monoid by enriching the give semigroup semi with the unit
module Bool : sig ... endMonoids over bool
module Int : sig ... endMonoids over int
module Option : sig ... endSemigroups over option types
module Endo : sig ... endSee Semigroup.Endo
module Dual : sig ... endSee Semigroup.Dual