Reader monad

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 Reader[I] extends Monad[({type M[O] = Function1[I, O]})#M] {
  def pure[A](a: A): Function1[I, A] = error("todo")
  def flatMap[A, B](f: A => Function1[I, B]): Function1[I, A] => Function1[I, B] = error("todo") 
}