Monad for the right side of Either.

gistfile1.scala

trait Monad[M[_]] {
  def pure[A](a: A): M[A]
  def flatMap[A, B](f: A => M[B]): M[A] => M[B]
  def map[A, B](f: A => B): M[A] => M[B] = flatMap(a => pure(f(a)))
}
 
class EitherRightMonad[L] extends Monad[({type M[R] = Either[L, R]})#M] {
  def pure[A](a: A): Either[L, A] = error("todo")
  def flatMap[A, B](f: A => Either[L, B]): Either[L, A] => Either[L, B] = error("todo") 
}