Re: Ada.Locales pseudo-string types

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Wed, 08 Aug 2012 14:14:26 +0300, Niklas Holsti wrote:

> On 12-08-08 11:09 , Dmitry A. Kazakov wrote:
>> On Wed, 08 Aug 2012 10:37:51 +0300, Niklas Holsti wrote:
>> 
>>> On 12-08-08 10:18 , Dmitry A. Kazakov wrote:
>>>> On Wed, 08 Aug 2012 10:04:37 +0300, Niklas Holsti wrote:
>>>>
>>>>> The rule does seem surprisingly rigid, for a value conversion. (The
>>>>> Annotated RM does not explain or motivate it.)
>>>>
>>>> Ada didn't appreciate structured type equivalence in earlier times. These
>>>> rules were designed before anonymous access types crept in.
>>>
>>> But we are talking about explicitly requested type conversions, not
>>> implicit type equivalence. As I understood it, at least.
>> 
>> Yes, but the validity of this conversion relies on an inferred equivalence
>> of the [sub]types of the elements.
> 
> No, I would rather think that the explicitly requested array-type
> conversion implies requests to convert the index [sub]types and the
> element [sub]types, too.

Yes, but the way this conversion is constructed is based on the assumption
that subtypes of the element are equivalent up to a conversion.

BTW, if you go that far you should also allow conversions between any array
types of convertible elements. E.g. between arrays of floats and arrays of
integers etc.

>> Ada considered them equivalent nominally.
> 
> Yes, but in order to be sure that the conversion requires no active
> machine code and can be done just by relabeling the type of a reference
> to the array.

This is one possible point of view, which is pretty weak.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de