MyMain.scala

object MyMain extends Application {
    abstract sealed class Either[+A,+B] {
        def map[C, D >: A](f:B => C) : Either[D,C]
        def flatMap[C, D >: A](f:B => Either[D,C]) : Either[D,C]
    }
    case class Right[A,B](b:B) extends Either[A,B] {
        def map[C, D >: A](f:B => C) = Right(f(b))
        def flatMap[C, D >: A](f:B => Either[D,C]) = f(b)
    }
    case class Left[A,B](a:A) extends Either[A,B] {
        def map[C, D >: A](f:B =>C) = Left(a)
        def flatMap[C, D >: A](f:B => Either[D,C]) = Left(a)
    }
    def div(a:Int, b:Int) = if(b==0) Left ("div by 0") else Right(a/b)
    val e = Right[String,Int](1)
    val g = for(x <- e; y <- div(x,0)) yield y
    println(g)
}