Example usage of Cats Bifunctor/Bifoldable/Bitraverse functions

CatsBi.scala

import cats._
import cats.data._
import cats.syntax._
import cats.implicits._

object CatsBi extends App {

  val fail = Left("failed")

  val ok = Right(123)

  // from Bifunctor

  def mybimap(e: Either[String, Int]): Either[String, String] = {
    e.bimap(_ + "!!", i => (i * 10).toString)
  }

  println(mybimap(fail))

  println(mybimap(ok))

  // from Bifunctor

  def myleftmap(e: Either[String, Int]): Either[String, Int] = {
    e.leftMap(_ + "!!!!!!!!")
  }

  println(myleftmap(fail))

  println(myleftmap(ok))

  // from Bifoldable

  def myfoldleft(e: Either[String, Int]): String = {
    e.bifoldLeft("either=")((acc, fail) => acc + fail, (acc, ok) => acc + ok)
  }

  println(myfoldleft(fail))

  println(myfoldleft(ok))

  // from Bifoldable, but this time using the Monoid of String to compose

  def myfoldmap(e: Either[String, Int]): String = {
    e.bifoldMap(identity, _.toString)
  }

  println(myfoldmap(fail))

  println(myfoldmap(ok))

  def myfold(e: Either[String, Int]): (String, Int) = {
    e.bifold
  }

  // from Bifoldable, but this time using the Monoid of String and Int to compose a tuple

  println(myfold(fail))

  println(myfold(ok))

  // from Bitraverse

  def mytraverse(e: Either[String, Int]): List[Either[Throwable, String]] = {
    e.bitraverse((f: String) => if (f.isEmpty) Nil else List(new Throwable(f)), (i: Int) => List(i.toString))
  }

  println(mytraverse(fail))

  println(mytraverse(ok))

  println(List(fail, Left(""), ok).flatMap(mytraverse))
}

output,txt

Left(failed!!)
Right(1230)
Left(failed!!!!!!!!)
Right(123)
either=failed
either=123
failed
123
(failed,0)
(,123)
List(Left(java.lang.Throwable: failed))
List(Right(123))
List(Left(java.lang.Throwable: failed), Right(123))