Derive semigroup instance for F[A]

Asked Dec 05 '20 at 03:57

Active Dec 05 '20 at 03:57

Viewed 70 times

It seems trivial to implement it on our own:

implicit def s[F[_]: Monad, A: Semigroup]: Semigroup[F[A]] = 
  Semigroup.instance((fa, fb) => for {
    fa <- fa
    fb <- fb
  } yield fa |+| fb)

But is it possible to derive it automatically? Kittens seems to work with case classes (at least I tried it for that case and it didn't work).

asked Dec 05 '20 at 03:57

Some Name

4

It is already in **cats**: https://typelevel.org/cats/api/cats/Applicative$.html#monoid[F[_],A](implicitf:cats.Applicative[F],implicitmonoid:cats.Monoid[A]):cats.Monoid[F[A]] – Luis Miguel Mejía Suárez Dec 05 '20 at 04:05
@LuisMiguelMejíaSuárez Thanks! Looked for it in the wrong place. – Some Name Dec 05 '20 at 04:09

0 Answers0