Nested

Similar to cats.data.Tuple2K, but for nested composition.

For instance, since both List and Option have a Functor, then so does List[Option[_]]. This is represented by this data type via the instantiation Nested[List, Option, *].

scala> import cats.Functor
scala> import cats.data.Nested
scala> import cats.implicits._
scala> val listOption: List[Option[Int]] = List(Some(1), None)
scala> val f: Int => String = i => (i * 2).toString
scala> Functor[List].map(listOption)(opt => opt.map(f))
res0: List[Option[String]] = List(Some(2), None)
scala> val nested: Nested[List, Option, Int] = Nested(listOption)
scala> val result: Nested[List, Option, String] = Functor[Nested[List, Option, *]].map(nested)(f)
scala> result.value
res1: List[Option[String]] = List(Some(2), None)