On Sun, Feb 18, 2007 at 05:06:33PM +0300, Bulat Ziganshin wrote:
Hello Marc,
Sunday, February 18, 2007, 5:21:36 PM, you wrote:
Why do I have to specify (Monad m) here again?
class (Monad m) =>> GetMV m a where
instance GetMV m c where
because you can find another way to ensure that m is monad. for example,
instance (MonadIO m) => GetMV m c where
if i not yet proposed you to read http://haskell.org/haskellwiki/OOP_vs_type_classes then now it is time to do it :)
I think I've read it once. But I'll do it again more thoroughly .. I'll try to explain why I don't get it yet class (Monad m) => GetMV m a where (1) tells that the first param called 'm' is an instance of class m, right? Then it doesn't matter wether I use instance GetMV m c where or instance GetMV <any name> c where If the class sepecification (1) forces m to be a monad, <any name> has to be one, too(?) When using your example (Monad IO): class (Monad m) => MonadIO m where liftIO :: IO a -> m a it it basically the same, isn't it? This declaration forces m to be monad.. which would't hurt if GHC would infer m beeing a monad automatically? Marc