On Sep 13, 6:25 pm, Maciej Piechotka <uzytkown...@gmail.com> wrote: > I started experiment with strict functors. I come to:
> > import Control.Exception > > import Foreign > > import Prelude hiding (catch) > > > data StrictMonad a = StrictMonad a deriving Show > > > instance Functor StrictMonad where > > f `fmap` StrictMonad v = return $ f v > > > instance Applicative StrictMonad where > > pure = return > > (<*>) = ap > > > instance Monad StrictMonad where > > return x = unsafePerformIO $ do > > (return $! x) `catch` \(SomeException _) -> return x > > return $! StrictMonad x > > StrictMonad v >>= f = f v > > It seems to be valid IMHO Functor and Monad (I haven't prove it) as long > as functions terminates. Here, I just believe you, and assume you mean that some non- terminating function would give problems to your strict functor, i.e. it wouldn't satisfy the functor/monad laws. Then, I also wonder if the functor you have is any different from an identity functor - I see why the monad could be strict. > Some time ago there was post stating that there is not possible strict > 'interesting' functor - I guess that the above is 'interesting' (and due > to halting problem I guess it is not possible to create strict Functor > which would deal with that problem). I'm no expert, but since a functor on the Hask category must work on all functions available there, it looks like you "proved" that yours is not a functor and can't be fixed; maybe, that means that no strict functor exist. Your function is probably valid in a different category, containing mostly the same objects but just total functions - if it is a valid category; I wonder what would happen when arrows in this category were applied on undefined, but maybe this means that objects in this category should not contain undefined as an element; at that point, you are in a strongly normalizing programming language and probably "strict" makes no sense. Then, I would also like to understand what exactly a strict functor is, in detail, and/or a link to the post you reference. Best regards Paolo _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
