[GHC] #15646: ghci takes super long time to find the type of large fractional number

[GHC]

#15646: ghci takes super long time to find the type of large fractional number
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        Reporter:  Johannkokos       |                Owner:
                                     |  JulianLeviston
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  GHCi              |              Version:  8.4.3
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by JulianLeviston):

 Update: Been working on this today; I've done the changes required in
 `BasicTypes.hs` and I'm on `Lexer.hs` changes now. It's going well,
 currently in the process of refactoring `readHexRational` to use a new
 function for reading the significand and exponent out of hex floating
 literals. (from `Util.hs`). Just finished doing that for `readRational`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15646#comment:31>
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