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cats.Monad

Monad is a subclass of Applicative. It declares an additional function, flatMap, as follows:

@typeclass trait Monad[F[_]] extends FlatMap[F] with Applicative[F]@typeclass trait FlatMap[F[_]] extends Apply[F] {
  def flatMap[A, B](fa: F[A])(f: A => F[B]): F[B]
}

This signature tells us that in order to produce F[B], flatMap will somehow have to extract A inside fa: F[A], and then call the function, f.

Previously, you saw that Applicative and mapN allow us to process several F[A] values in parallel, and combine them into a single F[B]. What Monad adds is the capability of processing F[] values in sequence: flatMap must process the F effect first, then call the f function.

Similar to Functor and map, many classes of the SDK already ...