Re: Ranges and (non)static constraints

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

On Thu, 16 Nov 2006 12:02:15 +0100, Maciej Sobczak wrote:

> type T is range 1 .. N;
> type U is new Integer range 1 .. M;
> 
> N must be static, but M does not have to.
> Why and what is the real difference between T and U?

Informally, the second is an abbreviation for:

   type <anonymous> is new Integer;
   subtype U is <anonymous> range 1..M;

so "range" refers to a subtype. On the contrary, in the first, "range"
refers a type. So the difference.

Is it real? I don't think so. I would eliminate this difference between
types and subtypes by allowing the latter to have a different
representation than the base. So the first should be also an abbreviation
for

   type <anonymous> is new Universal_Integer;
   subtype T is <anonymous> range 1..N;

That would make both legal (or, maybe, illegal (:-)).

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