DefinitionOfMonad.scala

 /*
    3 Monad laws

    1. Right identity: pure(a).flatMap(func) == func(a)
    2. m.flatMap(pure) = m
    3. m.flatMap(f).flatMap(g) = m.flatMap(x => f(x).flatMap(g))
   */

  trait MyMonad[F[_]] {

    def pure[A](a: A): F[A]

    def flatMap[A, B](fa: F[A])(f: A => F[B]): F[B]

    // all monads are functors because we can define map in terms of pure and flatMap
    def map[A, B](fa: F[A], f: A => B): F[B] = flatMap(fa)(a => pure(f(a)))
  }