[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 nomeata):

 I follow ekmett’s argument that Monoid to [] is like semigroups to ?, and
 to me it makes sense of have a type for non-empty sets in base. (If having
 a slim base were a goal, then maybe not, but I don’t see that being a goal
 for the community in general).

 But it is true that things are harder to fix once they are in base, so we
 should aim to pick the “right” implementation. According to
 https://wiki.haskell.org/Non-empty_list#Packages there are 6(!)
 implementations of non-empty lists on hackage. I did not look at them
 right now, so I’ll lazily pose the question: Is there any good reason to
 prefer any of these over the implementation from `semigroups`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10365#comment:36>
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