Behavior change of Data.Char

[Simon Peyton Jones]

It'd be good to document this condition/invariant in the Haddocks, wouldn't it?!

Simon

|  -----Original Message-----
|  From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
|  Herbert Valerio Riedel
|  Sent: 19 February 2015 10:42
|  To: Kazu Yamamoto
|  Cc: libraries at haskell.org; ghc-devs at haskell.org
|  Subject: Re: Behavior change of Data.Char
|  
|  On 2015-02-19 at 06:19:18 +0100, Kazu Yamamoto (山本和彦) wrote:
|  > It seems to me that some characters of GHC 7.10.1RC2 behave
|  > differently from those of GHC 7.8.4:
|  >
|  >                           7.8.4   7.10.1RC2
|  > isLower (char 170)        True    False
|  
|  Fwiw, the motivation for that particular change may be (I'm just
|  guessing here) to have the following condition hold:
|  
|    \c -> isLower c `implies` (not . isLower . toUpper) c
|  
|  i.e. if something is 'lower-case', then applying 'toUpper' should
|  result in a character that is not 'lower-case' anymore. This didn't
|  hold with 7.8.4's Unicode 6, but now holds with 7.10.1's Unicode 7
|  definitions.
|  
|  Cheers,
|    hvr
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