Re: Array Help?

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

On Wed, 29 Feb 2012 13:24:10 -0500, Robert A Duff wrote:

> Ludovic Brenta <ludovic@ludovic-brenta.org> writes:
> 
>> Doesn't that preclude slices that don't start at 'First?
> 
> Yes.

Too bad, yet another source of silly exceptions.

>> Supposing your declarations, can you call
>>
>> procedure Foo (Param : in out Integer_Array);
>>
>> like this:
>>
>> declare
>>    A : Integer_Array (1 .. 10) := (others => 0);
>> begin
>>    Foo (A (3 .. 8));
>> end;
>>
>> ?
> 
> That will raise C_E.  IMHO, that's a language design flaw -- inside
> Foo, Param'First ought to be 1.

Nope. Consider index of an enumeration type.

> The fact that Foo can see that
> it came from a slice is a leak of abstraction.

There is no leak, but a misuse of a cardinal index as if it were ordinal
number. This is typical for broken languages like C, but Ada was always
better.

What you want is something like:

   A (Index_Type'Val (1))  -- The first element of A

rather than

   A (1)  -- The element of A at the position corresponding to 1

Probably, the language should have a special syntax for that. Beloved []
brackets could suffice for the job:

   A [<universal-integer>]

could denote the array element by its position rather than by the index.

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