[GHC] #10190: Add a Monad instance for ((,) w)

[GHC]

#10190: Add a Monad instance for ((,) w)
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        Reporter:  fumieval          |                   Owner:
            Type:  bug               |                  Status:  patch
        Priority:  normal            |               Milestone:
       Component:  Core Libraries    |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by ekmett):

 No objection from me.

 This has passed the libraries@ proposal process on at least 2 separate
 occasions in recent memory, but had been blocked by the fact that Monoid
 wasn't in scope where the Monad class was defined.

 We have the compatible Applicative instance.

 I had honestly thought we already had the instance in 7.10.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10190#comment:3>
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