[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 rockbmb):

 Replying to [comment:14 Ashley Yakeley]:
 > 1. As written, the proposed change eliminates non-base-10 Fixed. Are we
 sure we want to do that?
 >
 > 2. 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, [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.

 I do not understand the point you make in 1., could you please elaborate?
 Regarding 2., I understand and agree. Would replacing a hardcoded
 `Integer` with `Integral a => ...` be sufficient?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15622#comment:16>
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