[Haskell-cafe] Proposal: Rational read

[Michael Orlitzky]

On 08/14/2016 06:54 PM, David Feuer wrote:
> Since decimal notation is defined in terms of fromRational, it seems a
> bit strange that the notation doesn't work for read::String->Rational.
> I'd be in favor of allowing it. I wouldn't expect too severe a
> performance penalty.
> 

One potential gotcha:

  ghci> read (show (1/3)) == (1/3)
  True
  ghci> read (show (1/3 :: Float)) == (1/3)
  False

When does it work? Is it platform-dependent?