Either... Left.. Right

Scala : Either, Left, Right Example

// Either... Left.. Right

scala>  def menu(day:String): Either[Int,String] = {
     |  if (day == "Sunday") Right("Fish Curry")
     |  else if (day == "Monday") Right("Veg Fry")
     |  else Left(0)

     |  }

menu: (day: String)Either[Int,String]

scala> println(menu("Sunday"))

Right(Fish Curry)

scala> println(menu("Monday"))

Right(Veg Fry)

scala> println(menu("Tuesday"))

Left(0)


  menu(input) match {
 case Left(a) => println("Left Answer is : " + a)
 case Right(b) => println("Right Answer is : " + b)

 }

 Right Answer is : Fish Curry

 scala> val c = menu("Monday")

c: Either[Int,String] = Right(Veg Fry)

scala> c.isRight

res3: Boolean = true

scala> c.isLeft

res4: Boolean = false

scala> val c = menu("Monday")

c: Either[Int,String] = Right(Veg Fry)

scala> c.isLeft

res5: Boolean = false

scala>

scala> c.isRight

res6: Boolean = true

scala> val input = "Sunday"

input: String = Sunday

scala> if (menu(input).isLeft) menu(input).left.map( a => println("Answer is : " + a))

res7: Any = ()

scala>  if (menu(input).isRight) menu(input).right.map( b => println("Answer is : " + b))

Answer is : Fish Curry

res1: Any = Right(())

scala> val c = menu("Monday")

c: Either[Int,String] = Right(Veg Fry)

scala> c

res3: Either[Int,String] = Right(Veg Fry)

scala> c.left.toOption

res8: Option[Int] = None

scala> c.right.toOption

res9: Option[String] = Some(Veg Fry)



def divideXByY(x: Int, y: Int): Either[String, Int] = {
      if (y == 0) Left("Dude, can't divide by 0")
      else Right(x / y)
  }

  // a few different ways to use Either, Left, and Right

  println(divideXByY(1, 0))

  println(divideXByY(1, 1))

  divideXByY(1, 0) match {
      case Left(s) => println("Answer: " + s)
      case Right(i) => println("Answer: " + i)
  }

}