Nope,
Other than possibly adding library clutter.

I have a package that provides many instances and common functions for ZipLists. Eventually I might stick it on hackage, but currently it's here: http://github.com/jvranish/ZipList

I really with there was a way to switch Applicative (or other) instances for list (or other) types.
Then we wouldn't have this problem.

- Job


On Fri, Oct 16, 2009 at 5:52 AM, Vladimir Reshetnikov <v.reshetnikov@gmail.com> wrote:
I find the following instance very convenient:

------------------------------------------------------------------------
import Data.Monoid
import Control.Applicative

instance Monoid a => Monoid (ZipList a) where
  mempty = pure mempty
  mappend = liftA2 mappend
------------------------------------------------------------------------

Any reason why it is not in the standard library?

Thanks,
Vladimir

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