import scalaz.syntax.ToIdOps

object example extends ToIdOps {
  type \/[+A, +B] = scalaz.\/[A, B]
  type -\/[+A] = scalaz.-\/[A]
  type \/-[+B] = scalaz.\/-[B]
  val \/ = scalaz.\/
  val -\/ = scalaz.-\/
  val \/- = scalaz.\/-
  type Either[+A, +B] = \/[A, B]
  type Left[+A] = -\/[A]
  type Right[+B] = \/-[B]
  val Either = \/
  object Left {
    def unapply[A, B](e: A \/ B): Option[-\/[A]] = Some(e).collect { case l@(-\/(_)) => l }
  }
  object Right {
    def unapply[A, B](e: A \/ B): Option[\/-[B]] = Some(e).collect { case r@(\/-(_)) => r }
  }
}

import example._

val e1: Either[String, Int] = "foo".left
e1 match {
  case Left(l) => Some(l)
  case Right(r) => None
}
val e2: Either[String, Int] = 2.right
for {
  x <- e1
  y <- e2
} yield x + y