[GHC] #10365: Implement Semigroup as a superclass of Monoid Proposal (Phase 1)

[GHC]

#10365: Implement Semigroup as a superclass of Monoid Proposal (Phase 1)
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        Reporter:  gidyn             |                Owner:  quchen
            Type:  feature request   |               Status:  patch
        Priority:  high              |            Milestone:  8.0.1
       Component:  libraries/base    |              Version:  7.10.1
      Resolution:                    |             Keywords:  report-impact
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1284
       Wiki Page:                    |
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Comment (by ekmett):

 Lemming: It is clear that any choice that includes it won't make you
 happy.

 However, randomly carving it up into two pieces and changing the API
 ensures that nobody who has existing code that supplies an `sconcat` in
 their instances winds up with code that will work across the transition.

 `semigroups` is the most downloaded package in all of Hackage, I don't
 like the idea of randomly bikeshedding the API here to get an end state
 that is less useful and which ensures work on the behalf of every package
 maintainer who currently implements `sconcat`.

 The transition story is better if we include it than if we don't, and the
 result is more usable out of the box.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10365#comment:33>
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