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Newsgroups: comp.lang.ada
Date: Fri, 28 Oct 2016 14:08:12 -0700 (PDT)
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Subject: Re: Bug in Ada - Latin 1 is not a subset of UTF-8
From: Shark8 <onewingedshark@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:32189
Date: 2016-10-28T14:08:12-07:00
List-Id: <comp.lang.ada>

On Tuesday, October 18, 2016 at 2:45:05 AM UTC-6, Dmitry A. Kazakov wrote:
> On 18/10/2016 10:23, G.B. wrote:
> > On 18.10.16 09:41, Dmitry A. Kazakov wrote:
> >> On 18/10/2016 01:25, G.B. wrote:
> >>> On 17.10.16 22:18, Lucretia wrote:
> >>
> >>> According to ISO 10646, UTF stands for UCS Transformation
> >>> Format. So, it's a format, suggesting a representation.
> >>>
> >>> On similar grounds, one could define a string subtype for
> >>> other types of objects, for example
> >>>
> >>>   subtype Number_String is String;
> >>
> >> You are wrong.
> >
> > The constraints on either UTF_String or or Number_String are
> > not expressible as simple Ada subtypes. They are given by
> > description and normative reference, respectively.
>=20
> In the case of UTF-8 it is not a constraint. "=C3=84" has different=20
> representations as Latin-1 and UTF-8 strings.
>=20
> Numeric character is a constraint expressible in Ada:
>=20
>     subtype Numeric is Character range '0'..'9';
>=20
> Numeric string constraint is not expressible, but it still a constraint.


You are wrong; it is expressible:
   -- Using your Numeric character subtype.
   Subtype Digits is String
    with Dynamic_Predicate =3D> (for all Ch of Digits =3D> Ch in Numeric);