[GHC] #13203: Implement Bits Natural clearBit

[GHC]

#13203: Implement Bits Natural clearBit
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        Reporter:  dylex             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  lowest            |            Milestone:
       Component:  libraries/base    |              Version:  8.0.2
      Resolution:                    |             Keywords:
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 vlopez):

 At least it should be documented that `clearBit` is undefined.

 For implementing `clearBit`, instead of doing a conditional
 `complementBit` on `testBit`, I  suggest doing a `complementBit` after
 `setBit`. This avoids branching entirely.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13203#comment:2>
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