[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 yalas):

 Replying to [comment:18 Scott Turner]:
 > Maybe we are talking about it because it has the rule
 > {{{
 > x ** 0 == 1
 > }}}
 I think it is completely safe to define:
 {{{
 _ ** (0:+0)    =  1 :+ 0
 }}}
 Because {{{exp $ log any_finite_number * (0:+0)}}} always equals
 {{{1:+0}}}.
 The only difference is for NaN, but {{{NaN**0 :: Double}}} equals {{{1}}}
 too.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8539#comment:20>
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