[GHC] #9238: Negative zero broken

[GHC]

#9238: Negative zero broken
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        Reporter:  augustss          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #7858, #9451      |  Differential Revisions:
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Comment (by simonpj):

 Replying to [comment:13 bgamari]:

 > simonpj, how do you think your suggestion should interact with the
 `litEq` rule? As far as I can tell this `PrelRule` is responsible for most
 of the floating-point pattern matches that we are seeing. As you
 essentially suggesting we disable `litEq` for floating-point types?

 Well, IF we agree that Core case expressions should not scrutinise
 floating point values, THEN
  * We should document that invariant, with explanation of why
  * We should make Core Lint check for it
  * And yes `litEq` (which generates such case expressions) should not do
 so for floating point values

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9238#comment:14>
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