On Wed, Jun 04, 2003 at 08:38:29PM +0200, Tomasz Zielonka wrote: > On Wed, Jun 04, 2003 at 11:15:30AM -0700, Hal Daume III wrote: > > > I'm trying to figure if there's any way I can use (say) monads to collect > > > values from a Functor. > > > > > > For example, suppose I have a tree of some values that supports fmap, is > > > there any way I can use the fmap function to collect a list of all the node > > > values? > > > > No, you need a fold to do that. > > Or a variant of Functor constructor class that I have proposed some time > ago on comp.lang.functional: > > class FunctorM t where > fmapM :: Monad m => (a -> m b) -> (t a -> m (t b)) > fmapM_ :: Monad m => (a -> m b) -> (t a -> m ()) > fmapM_ f t = fmapM f t >> return () > > instance FunctorM [] where > fmapM = mapM > fmapM_ = mapM_
I am sorry, I misunderstood the problem. Best regards, Tom -- .signature: Too many levels of symbolic links _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
