[GHC] #8539: Data.Complex shouldn't use default implementation of (**)

[GHC]

#8539: Data.Complex shouldn't use default implementation of (**)
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        Reporter:  jjaredsimpson     |            Owner:
            Type:  bug               |           Status:  patch
        Priority:  low               |        Milestone:
       Component:  Prelude           |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  Incorrect result  |       Difficulty:  Easy (less than 1
  at runtime                         |  hour)
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by Scott Turner):

 > But wolphramalpha gets ​0, ​infinity or ​indeterminate.
 which agrees with what I said earlier,
 > If the real part of y is positive, then the result should be 0. If the
 real part is negative, then the result should be Infinity. If y is
 imaginary, the result should be NaN.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8539#comment:14>
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