Proposal: Remove Semigroup and Monoid instances for Data.Map, Data.IntMap, Data.HashMap

Henning Thielemann lemming at
Wed Feb 14 01:35:58 UTC 2018

On Tue, 13 Feb 2018, David Feuer wrote:

> 1. Deprecate the Semigroup and Monoid instances for Data.Map.Map,
> Data.IntMap.IntMap, and Data.HashMap.HashMap in the next releases of
> containers and unordered-containers.
> 2. Remove the deprecated instances.
> 3. After another several years (four or five, perhaps?), make a major
> release of each package in which the instances are replaced with the
> following:

I like the plan. Re-adding with Semigroup superclass would prevent silent 
re-interpretation of code if it is generic.

More information about the Libraries mailing list