sample code for Cats MTL MonadChronicle

monadChronicle.sc

import cats.Monad
import cats.data.{Chain, Ior}
import cats.mtl.MonadChronicle
import cats.syntax.applicative._
import cats.syntax.functor._
import cats.mtl.instances.chronicle._
import cats.syntax.traverse._
import cats.instances.list._

def func[F[_]: Monad](n: Int)(implicit F: MonadChronicle[F, Chain[Int]]): F[Int] =
  if      (n > 4) F.confess(Chain(-n))     // FunctorRaise#raise 相当
  else if (n > 2) F.dictate(Chain(n)) as n // FunctorTell#tell 相当
  else            n.pure[F]

type IorC[A] = Ior[Chain[Int], A]

(1 to 1).toList.traverse(func[IorC]) // Right(List(1))
(1 to 2).toList.traverse(func[IorC]) // Right(List(1, 2))
(1 to 3).toList.traverse(func[IorC]) // Both(Chain(3),List(1, 2, 3))
(1 to 4).toList.traverse(func[IorC]) // Both(Chain(3, 4),List(1, 2, 3, 4))
(1 to 5).toList.traverse(func[IorC]) // Left(Chain(3, 4, -5))
(1 to 6).toList.traverse(func[IorC]) // Left(Chain(3, 4, -5))