Re: The extension of Is_Basic to unicode (about AI12-0260-1)

["Randy Brukardt" <randy@rrsoftware.com>]

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"J-P. Rosen" <rosen@adalog.fr> wrote in message 
news:palsmv$g18$1@gioia.aioe.org...
> Le 11/04/2018 à 16:32, Dan'l Miller a écrit :
>>> True if Item is a basic letter. A basic letter is a character that
>>> is in one of the ranges 'A'..'Z' and 'a'..'z', or that is one of
>>> the following: 'Æ', 'æ', 'Ð', 'ð', 'Þ', 'þ', or 'ß'.
>> If this Ada-specific definition of this is-basic/base-Latin-letter
>> property is the official normative list, then it seems rather
>> arbitrary and capricious, not conforming to Unicode or to linguistic
>> reality.
>>
>> In Unicode-speak's terminology/jargon, the definition of base
>> character at https://definedterm.com/a/definition/160575 would admit
>> quite a few more, [...]
> The above Is_Basic is about Character, and is defined only when using
> Latin-1. Unicode is a different standard.

Moreover, its definition is historical -- it was defined this way for Ada 
95, and whether or not that would be the correct definition had it been 
defined in 2018 is irrelevant. Changing the definition would potentially 
silently break programs that use it. There are a number of things in 
Ada.Characters.Handling that aren't correct for Unicode purposes, one of 
them is even called out by the third note in A.3.2.

                      Randy.