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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Locales pseudo-string types
Date: Wed, 08 Aug 2012 14:52:01 +0300
Organization: Tidorum Ltd
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Date: 2012-08-08T14:52:01+03:00
List-Id: <comp.lang.ada>

On 12-08-08 11:35 , Dmitry A. Kazakov wrote:
> On Wed, 08 Aug 2012 11:17:46 +0300, Niklas Holsti wrote:
> 
>> For value conversions, including "in" parameters, the exact match could
>> be replaced by a static check that the constraints on the source
>> elements are the same as or stronger than those on the target elements.
>> This would allow Ada.Text_IO.Put (String (Some_Country_Code)).
>>
>> For "out" parameters, there could be a static check that the constraints
>> on the actual (source) array elements are the same as or weaker than
>> those on the formal (target) array elements.
>>
>> For "in out" parameters, the present static-match rule would be kept, as
>> the logical conjunction of the "in" and "out" rules.
> 
> 1. You cannot check that statically because the constraint of the subtype
> can be dynamic.

I meant (of course!) that the conversion would be allowed only if the
strengths of the constraints can be checked statically, using similar
kinds of rules as are now used for "statically matching" subtypes and
constraints. In effect, the bounds of the ranges would have to match
exactly, or be static expressions with values in the necessary order
relationships.

> 2. It is extremely uncomfortable to have legality dependant on the
> constraint and the parameter mode. It is worse than just inference it is in
> effect weakly typing.

We won't agree on that one.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .