Scalaz Comonad

Comonad is a Cobind that also has copoint method. Scalaz defines Comonad[F[_]] with copoint abstract method.

def copoint[A](p: F[A]): A

Note that when point method of Monad turns A to F[A], copoint method of Comonad turns F[A] to A.

Since NonEmptyList is Comonad I’m gonna demonstrate it on NonEmptyList:

import scalaz.NonEmptyList._
import scalaz.syntax.comonad._

display(NonEmptyList(1, 2, 3).copoint, """ NonEmptyList(1, 2, 3).copoint """)

Output

NonEmptyList(1, 2, 3).copoint    1