Behavior change of Data.Char

[Herbert Valerio Riedel]

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