Ertugrul Söylemez wrote:
For another the same can be achieved with free monads in a more transparent and flexible manner:
import Control.Monad.Free.Class
data PromptF a b x = PromptF (b -> x) a deriving (Functor)
More accurately,
data PromptF' p x = forall a. PromptF (a -> x) (p a)
(with the obvious Functor instance).
Are we talking about the same PromptT here? I was assuming this one: https://hackage.haskell.org/package/prompt-0.1.1.2/docs/Control-Monad-Prompt....
No, I'm talking about https://hackage.haskell.org/package/MonadPrompt-1.0.0.5/docs/src/Control-Mon... (FWIW, I did mention the package name in my mail.) The type in the prompt package does not seem to offer the main benefit I mentioned, namely that the prompt value encodes the type of the return value of the `prompt` action; indeed, `prompt` in the prompt package has type prompt :: MonadPrompt a b m => a -> m b in contrast to prompt :: MonadPrompt p m => p a -> m a in MonadPrompt.
Even if not, it seems to me that it should be an abstraction layer above free monads. It could be a very thin layer around F/FT. That would facilitate reuse.
MonadPrompt is a very thin standalone package... I would be quite sad to lose that property. Cheers, Bertram