Re: type and subtype

Dmitry A. Kazakov wrote: 

I think that Ludovic's view is more consistent: checks are just a part of
the conversion which otherwise is an identity function, because *presently*
the representation is required to be same. But representation is an
implementation detail and thus cannot count. Moreover it is very desirable
to allow subtypes having different representations.


Try this with your favorite compiler:

Ada.Text_IO.Put_Line
   (Item => "Integer'Size =" & Integer'Image (Integer'Size) ):
Ada.Text_IO.Put_Line
   (Item => "Natural'Size =" & Integer'Image (Natural'Size) ):

You're likely to get something like

Integer'Size = 32
Natural'Size = 31

because representations of subtypes are not required to be the same.

We can also consider

type Rec (Length : Positive) is record
   V : String (1 .. Length);
end record;

subtype Small is Rec (Length =>     1);
subtype Big   is Rec (length => 1_000);

where Small and Big have significantly different representations. Then there are subtypes of variant record types with discriminants that select different variants. 
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n:;Jeffrey Carter
email;internet:jeffrey_r_carter-nr [commercial-at] raytheon [period | full stop] com
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