[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 Ashley Yakeley):

 1. The time library uses Fixed, so I'm not sure the Hackage search was
 good?

 2. As written, the proposed change eliminates non-base-10 Fixed. Are we
 sure we want to do that?

 3. If we're considering breaking changes to Data.Fixed, the more urgent
 need (imo) is to generalise the representation type, which is currently
 hard-coded as Integer.

 Touching both points 2 and 3,
 [https://en.wikipedia.org/wiki/Q_(number_format) Q formats] are fixed-
 point with a given number of fractional lower bits. It would be useful to
 be able to represent these.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15622#comment:14>
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