[Haskell-cafe] Re: GUI programming

[Victor Nazarov]

On Wed, Feb 3, 2010 at 4:11 PM, Heinrich Apfelmus
<apfelmus at quantentunnel.de> wrote:
> Victor Nazarov wrote:
>> data Behaviour a =
>>   forall b. BBind (Behaviour b) (b -> Behaviour a)
>>   | BIO (IO a)
>>   | forall obj. GObjectClass obj => BWaitEvent (Event obj) (Behaviour a)
>>
>> instance Monad Behaviour
>>  where action >>= generator = BBind action generator
>>        return a = BIO (return a)
>>
>> instance MonadIO Behaviour
>>  where liftIO action = BIO action
>>
>> runBehaviour :: Behaviour a -> IO a
>> runBehaviour (BBind (BWaitEvent event after) f) = runBehaviour
>> (BWaitEvent event (after >>= f))
>> runBehaviour (BBind (BIO a) f) = a >>= \x -> runBehaviour (f x)
>> runBehaviour (BBind (BBind a f) g) = runBehaviour (a >>= (\x -> f x >>= g))
>
> Just a minor note: you can somewhat clean up your code by using a
> generic monad, as implemented in my cabal package  operational
>
>   http://hackage.haskell.org/package/operational
>
> and described in
>
>   Heinrich Apfelmus. The Operational Monad Tutorial.
>   In http://themonadreader.wordpress.com/2010/01/26/issue-15/
>
>

Thank you.

It seems relevant. I'll have a look at it.

Speaking about packages. What is current community status of monad
transformers packages. I'm using MonadIO class and there are mtl,
monads-fd, monads-tf packages that provide it. I personally prefer
type families to functional dependencies. Should I use monads-tf, or
should I stick to mtl?


-- 
Victor Nazarov