Merijn Verstraaten
I would like to propose adding a newtype wrapper (with all relevant instances) for Map and IntMap (if I missed any other applicable type in containers, let me know).
This newtype should differ in Monoid/Semigroup instance from Map/IntMap by switching:
Ord k => Semigroup (Map k v) Ord k => Monoid (Map k v)
to:
(Ord k, Semigroup v) => Semigroup (Map k v) (Ord k, Monoid v) => Monoid (Map k v) or (Ord k, Semigroup v) => Monoid (Map k v)
Any opinions on the overall idea? Opinions on which Monoid instance? Bikeshed for the newtype names?
For what it's worth, I provide precisely this in my monoidal-containers package [1]. Also, Edward Kmett provides a similar idea in his reducers package [2]. Cheers, - Ben [1] https://hackage.haskell.org/package/monoidal-containers [2] https://hackage.haskell.org/package/reducers-3.12.1/docs/Data-Semigroup-Unio...