English
If α is a Commutative Monoid, then Filter α is a Commutative Monoid under pointwise multiplication.
Русский
Если α коммутативный моноид, то Filter α — коммутативный моноид под точечным умножением.
LaTeX
$$$\text{Filter}(\alpha)$ is a CommMonoid when $\alpha$ is a CommMonoid.$$
Lean4
/-- `Filter α` is a `CommMonoid` under pointwise operations if `α` is. -/
@[to_additive /-- `Filter α` is an `AddCommMonoid` under pointwise operations if `α` is. -/
]
protected def commMonoid [CommMonoid α] : CommMonoid (Filter α) :=
{ Filter.mulOneClass, Filter.commSemigroup with }