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From: "G.B." <bauhaus@futureapps.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Bug in Ada - Latin 1 is not a subset of UTF-8
Date: Tue, 18 Oct 2016 19:35:32 +0200
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Date: 2016-10-18T19:35:32+02:00
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On 18.10.16 18:35, Dmitry A. Kazakov wrote:
> No invariant can make Latin-1 A-umlaut UTF-8 A-umlaut.

Who would ever want to do that?

Before I/O, there is nothing. UTF_8_String is for encoding
and decoding subprograms of Ada. For them to be successful,
a predicate could be used to express the set of values that
can be parsed. It so happens that its members are officially
said to be in encoded form.

To get a subset U from a set S, you apply a constraint
to S. That's not (easily) expressible in Ada in this case.
But if it is, with the help of a predicate, the we can
say that UTF_8_String is-a "constrained" String because
their sets are.