Re: ADA.STRINGS.INDEX_ERROR : a-strunb.adb:782

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

On 19/01/2018 02:10, Randy Brukardt wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:p3qe4m$t5n$1@gioia.aioe.org...
>> On 18/01/2018 14:08, J-P. Rosen wrote:
>>
>>> If the user were allowed to define identifiers with a quote, these would
>>> not be true any more, and there would be no benefit in using a
>>> distinctive syntax.
>>
>> As if there were any benefit of.
> 
> The benefit is that these things can express ideas that aren't possible for
> ordinary subprogram calls.

That does not justify special syntax. E.g. initialization cannot be 
expressed as a subprogram call either, nevertheless there is no special 
syntax for declaration of objects with non-null initialization.

> To express Subtype'First as a function, one would
> have to have some sort of meta-type (a subtype parameter).

I don't think this is related.

(However I am glad that you begin to see subtypes as proper types. (:-))

> You'd also have
> to allow "univeral_integer" and the like as expressible data types (meaning
> that you'd have to decide what they mean at runtime). All things that could
> be done -- in a new language -- but it would be extremely difficult to
> define such things and keep compatibility with existing Ada.

You know that I disagree with this. In my view it is possible to allow

1. interfaces and class-wides for scalar types

2. cloning of type hierarchies by Ada 83 style

    type Y is new X;

Universal_Integer would be a parent of any integer type in its hierarchy.

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