Re: Inferring array index type from array object

[Warren <ve3wwg@gmail.com>]

Niklas Holsti expounded in news:88f9osFmcmU1@mid.individual.net:

> Warren wrote:
>> Niklas Holsti expounded in news:88ec2vF3uqU1@mid.individual.net:
>>> Dmitry A. Kazakov wrote:
>>>> On Wed, 23 Jun 2010 00:30:23 -0700 (PDT), Maciej Sobczak wrote:
>> ..
>>>>> 2. Is it possible to declare the index variable without hardcoding
>>>>> the index type (that is, to infer it from the array object)?
>>>> No, without improving the type system. E.g. introducing abstract
>>>> index types, and abstract range types (or more general sets of index
>>>> types), and abstract composite types like arrays.
>>> I don't think such large language changes would be necessary. The 
>>> expression S'Range gives the compiler all the information about the
>>> type and its constraints, so I see no reason why Ada could not be
>>> extended simply to allow S'Range in a variable declaration, as in the
>>> above quoted "I : S'Range". The declared variable "I" would have the
>>> same (sub)type as the loop counter in "for I in S'Range loop ...".
>> 
>> I think most would agree that this is a "convenience" feature.
> 
> Yes, but in other contexts, when we advocate Ada, we often make a big 
> point of the "convenience" of the 'Range attribute for arrays, such as 
> "No need to pass extra parameters for array index bounds, just use 
> 'Range". The suggestion to let variables be declared by the "type" 
> S'Range (or, if desired, a new attribute S'Index_Type) has a similar 
> advantage (but a weaker one, I admit).

But how far down that road do you want to go? This is
the crux of the issue. 

I'd find ++X or X += n convenient. But should that be 
implemented in Ada?  I'm ok with leaving it out.

At some point, you have to draw a line in the sand.

Warren