2011/6/8 Brandon Allbery <allbery.b@gmail.com>

On Tue, Jun 7, 2011 at 16:16, Arnaud Bailly <arnaud.oqube@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.

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