[GHC] #15622: Generalize `E{0,1,2,3,6,9,12}` from `Data.Fixed`

[GHC]

#15622: Generalize `E{0,1,2,3,6,9,12}` from `Data.Fixed`
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        Reporter:  rockbmb           |                Owner:  rockbmb
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Core Libraries    |              Version:  8.4.3
      Resolution:                    |             Keywords:  base,
                                     |  Data.Fixed
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Bodigrim):

 `Compose` itself makes no difference, of course. The instance from your PR
 is equivalent to `resolution = (10 ^) . natVal . Compose`. My suggestion
 is to put `resolution = natVal . Compose`, which makes us able to express
 desired accuracy both in decimal (`E 1000`) and binary (`E 1024`) digits,
 as well as in any other base.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15622#comment:21>
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