Re: Arrays in Ada 2012

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:ohat3q$lon$1@gioia.aioe.org...
> On 08/06/2017 02:51, Randy Brukardt wrote:
>
>> The definition of 'Size is stupid, so you need rounding like that to be
>> portable.
>
> You mean being bit size or being kind of weakly typed (universal integer). 
> I disagree on the first and agree on the second. It possibly should be 
> overloaded:
>
>   function 'Size (...) return Storage_Count; -- Storage units
>   function 'Size (...) return Storage_Size;  -- Bits

The definition of 'Size is stupid, because it's neither the bit size nor the 
usual allocation size, but a weird hybrid of both. It's primary effect is to 
provide a lower bound for packing, which is hardly ever what you want to 
limit. (Why would you want to prevent someone from packing some component?)

And 'Size has no effect at all on what you can write in other rep. clauses, 
like 'Component_Size and record representations. So setting 'Size almost 
never does what you want (unless the compiler tries to be friendly -- but 
that runs into problems with the required default value of Size).

Thus GNAT (and soon Ada) introduced 'Object_Size, which gives the UPPER 
bound on the allocated size. A much more useful thing to bound - you can 
ensure that type Byte really only uses a byte, for instance.

                                    Randy.