[GHC] #10067: The Read Integer instance is too slow

[GHC]

#10067: The Read Integer instance is too slow
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        Reporter:  redneb            |                   Owner:
            Type:  feature request   |                  Status:  patch
        Priority:  low               |               Milestone:
       Component:  Core Libraries    |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D645
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Comment (by redneb):

 I only ommited `Natural` because the read instance for it relies on the
 read instance of `Integer` and therefore it will befenefit from my patch
 anyway. But I agree that it would be a good idea to start treating
 `Natural` as a first class citizen.

 So what's the policy here? Do I need to `CPP`/`#ifdef` this, or is that
 unnecessary since they are from the same package anyway?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10067#comment:5>
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