I believe this is the App newtype in the monoids package [0].
Erik
[0] https://hackage.haskell.org/package/monoids-0.3.2/docs/
Data-Monoid-Applicative.html#t:App
On 5 September 2016 at 20:54, Brian Hurt
This may be a stupid question, but I'm wondering why the following instance isn't in prelude:
instance (Applicative m, Monoid a) => Monoid (m a) where mempty = pure mempty mappend a b = mappend <$> a <*> b
?
I ask, because being able to use a WriterT (IO ()) STM a to debug complex STM expressions would be really nice. But it depends upon IO () being a monoid.
Brian
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