haskell-semigroups (Anything that associates)

In mathematics, a semigroup is an algebraic structure consisting of

a set together with an associative binary operation. A semigroup

generalizes a monoid in that there might not exist an identity

element. It also (originally) generalized a group (a monoid with all

inverses) to a type where every element did not have to have an

inverse, thus the name semigroup.