Monoid package:invertible
Invariant monoidal functors.
This roughly corresponds to
Control.Applicative, but exposes a
non-overlapping API so can be imported unqualified. It does, however,
use operators similar to those provided by contravariant.
Invariant monoidal functor. This roughly corresponds to
Applicative, which, for covariant functors, is equivalent to a
monoidal functor. Invariant functors, however, may admit a monoidal
instance but not applicative.
Monoidal functors that allow choice.