[GHC] #14425: approxRational is wrong when (rat - eps) overflows in negative direction

[GHC]

#14425: approxRational is wrong when (rat - eps) overflows in negative direction
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           Reporter:  danielk        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  8.2.1
  libraries/base                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 This program is wrong. The second output should be 0 % 1.


 {{{
 import Data.Ratio

 main = do
   print (approxRational (0 % 1 :: Ratio Int) (1 % 10)) -- 0%1, correct
   print (approxRational (0 % 1 :: Ratio Word) (1 % 10)) -- 1%1, incorrect
 }}}

 The problem is that (rat-eps) overflows in the negative direction (see
 [http://hackage.haskell.org/package/base-4.10.0.0/docs/src/Data.Ratio.html#approxRational
 source]).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14425>
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