TypeHierarchy.scala

TypeHierarchy.scala

// A classic definition of functor, applicative and monad. 
trait Functor[T[_]] {
  def apply[A](a: A): T[A]
  def map[A, B](f: A => B)(a: T[A]): T[B]
}
 
trait Applicative[T[_]] extends Functor[T[_]] {
  def pmap[A, B](f: T[A => B])(a : T[A]) : T[B]
}
 
trait Monad[T[_]] extends Functor[T[_]] {
  def flatMap[A, B](f: A => T[B])(a: T[A]) : T[B]
}