[GHC] #12665: Make Read instances faster, and make them fail fast

[GHC]

#12665: Make Read instances faster, and make them fail fast
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        Reporter:  dfeuer            |                Owner:  dfeuer
            Type:  feature request   |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Core Libraries    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by int-e):

 more prototypes for conversion from digits to an integer can be found
 here: http://int-e.eu/~bf3/haskell/FromDigits.hs ... `valInteger'` is the
 most interesting one of the bunch, and according to some preliminary
 testing, also the most efficient.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12665#comment:10>
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