This is a neat idea, and potentially useful. +1. If this gets through, the instance should include documentation describing how it works (probably mentioning zipWith) and contrasting it with the Monoid [a] instance. On 25/07/15 23:50, Christopher Allen wrote:
http://hackage.haskell.org/package/base-4.8.1.0/docs/Control-Applicative.htm...
There's a Monoid that matches what the Applicative for ZipList does that seems to be missing.
instance Monoid a => Monoid (ZipList a) where mempty = pure mempty mappend = liftA2 mappend
It's been brought up before:
https://mail.haskell.org/pipermail/haskell-cafe/2009-October/067861.html
Not only is it useful when it's the Monoid you want, but it serves an educational purpose for highlighting the relationship between Monoid and Applicative as well.
Are there any good reasons not to have it?
I'd like to limit discussion to two weeks.