MONOID
signature
The MONOID
signature establishes a type $t$ along
with an associative binary function $f$ and identity $I$ such that
$(t, f, I)$ is a monoid.
type t
val I : t
val f : t * t → t
val toString : t → string
type t
val I :
t
val f :
t * t → t
val toString :
t → string