register.scala

// three ways of expressing registration and sending confirmation e-mail in scala

(R.register _)
  .andThen(_
    .map(C.withConfirmable)
    .map(_ >>= { confirmable => OptionT.liftF(C.sendConfirmationInstructions(confirmable)) })
  )
  .andThen(_ >>= { _ => Ok() })
  .apply(form)

// using for-comprehension
val registered = for {
  user <- OptionT.liftF(R.register(form))
  confirmable <- C.withConfirmable(user)
  sent <- OptionT.liftF(C.sendConfirmationInstructions(confirmable))
} yield sent
registered.value >>= { _ => Ok() }

// and bind
val registered2 = OptionT.liftF(R.register(form)) >>=
  C.withConfirmable >>=
  { confirmable => OptionT.liftF(C.sendConfirmationInstructions(_)) }
registered2.value >>= { _ => Ok() }