ConcatAll concatenates all values using the monoid and the default empty value.

Fold concatenates all values using the monoid and the default empty value.

FunctionMonoid forms a monoid as long as you can provide a monoid for the codomain.

MakeMonoid creates a monoid given a concat function and an empty element.

Reverse returns the dual of a `Monoid`, obtained by swapping the arguments of `Concat`.