Beautiful. Can we have a version on hackage?
On Thu, Jul 16, 2009 at 5:56 PM, Job Vranish<jvran...@gmail.com> wrote: > I was needing a way to zip generic data structures together today and was > very annoyed to find that there is no Zippable class, or variant there of. > > So I made my own: > > class (Foldable f, Functor f) => Zippable f where > fmaps :: (Foldable g) => g (a -> b) -> f a -> f b > fmaps' :: [a -> b] -> f a -> f b -- to save a step on instance > implementation > zipWith :: (a -> b -> c) -> f a -> f b -> f c > zip :: f a -> f b -> f (a, b) > unzip :: f (a, b) -> (f a, f b) > > fmaps fs a = fmaps' (toList fs) a > fmaps' fs a = fmaps fs a > zipWith f a b = fmaps (fmap f a) b > zip = zipWith (,) > unzip a = (fmap fst a, fmap snd a) > > instance Zippable [] where > fmaps' (fx:fs) (x:xs) = fx x : fmaps' fs xs > fmaps' _ _ = [] > > --The fmaps function is also quite handy as a replacment for zipWith3, > zipWith4, etc... > --For example: > > x = [1, 3, 5, 7, 3] > y = [6, 9, 3, 1, 4] > z = [2, 4, 0, 8, 2] > test = fmap (,,) x `fmaps` y `fmaps` z > -- > [(1,6,2),(3,9,4),(5,3,0),(7,1,8),(3,4,2)] > > --you can also throw in a functor instance to remove the dependency on the > Functor class, but it > -- might not be worth it: > instance (Zippable f) => Functor f where > fmap f a = fmaps (repeat f) a > > > Is there any good reason that there isn't something like this in the > standard libraries? Or, as far as I can tell, on hackage? > If not, then maybe I'll stick it on hackage. > > - Job Vranish > > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
