add method on object CommutativeApplicative to get CommutativeMonoid

[johnynek]

object CommutativeApplicative {
  def commutativeMonoidFor[F[_]: CommutativeApplicative, A: CommutativeMonoid]: CommutativeMonoid[F[A]]
}

object CommutativeApply {
  def commutativeSemigroupFor[F[_]: CommutativeApply, A: CommutativeSemigroup]: CommutativeSemigroup[F[A]]
}

These show how UnorderedFoldable and UnorderedReducible can have a def unorderedTraverse_ and def unorderedSequence_.

Which can be useful on things like hash-sets and hash-maps (and heaps).

[alexeygorobets]

So it is like

object CommutativeApplicative {
  def commutativeMonoidFor[F[_]: CommutativeApplicative, A: CommutativeMonoid]: CommutativeMonoid[F[A]] =
    new CommutativeMonoid[F[A]] {
      override def empty: F[A] = CommutativeApplicative[F].pure(CommutativeMonoid[A].empty)

      override def combine(x: F[A], y: F[A]): F[A] = {
        CommutativeApplicative[F]
          .map2(x, y)(CommutativeMonoid[A].combine)
      }
    }
}

object CommutativeApply {
  def commutativeSemigroupFor[F[_]: CommutativeApply, A: CommutativeSemigroup]: CommutativeSemigroup[F[A]] =
    new CommutativeSemigroup[F[A]] {
      override def combine(x: F[A], y: F[A]): F[A] = {
        CommutativeApply[F]
          .map2(x, y)(CommutativeSemigroup[A].combine)
      }
    }
}

or I am missing something?

[johnynek]

I think that’s it.