I've definitely wanted it in the past, and have even implemented limited
versions of it before. I'd be open to adding it to Data.Containers in
mono-traversable[1].
[1]
http://www.stackage.org/haddock/nightly-2015-01-20/mono-traversable-0.7.0/Da...
On Tue Jan 20 2015 at 4:34:00 AM Konstantine Rybnikov
Hi!
I'm working with a lot of HashMap's and it's very frustrating how many times I've "lost" my data because of usage of either a Monoid instance of a HashMap (which is defined as H.union, which, upon collision, takes value from first hm and discards from second), or just using fromList in the wrong place. Whereas the data I'm working is is mostly defined as (Monoid v => HashMap k v), so what I need "by default" is actually something like `H.unionWith (<>)`.
What I was wondering is this: is something like MonoidHashMap is desired to be in unordered-containers, or is this use-case only popular in my programs? I'm asking because I have a feeling that this thing might be useful quite a lot for others also. If not -- sorry for bothering :)
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