[Haskell-cafe] Non-advanced usage of Type classes

[Brandon Allbery]

On Tue, Jun 7, 2011 at 16:16, Arnaud Bailly <arnaud.oqube at gmail.com> wrote:
> For example, while designing some program (a game...) I defined a type class
> thus:
>
>> class (Monad io) => CommandIO io where
>>  readCommand  :: io Command
>>  writeResult  :: CommandResult -> io ()

This is in fact one of the reasons to use type classes.  In fact,
you'll find a somewhat more general variety of it on Hackage in a
couple of forms, the one I'm most familiar with being MonadPrompt.