Re: 'Base

[Martin Dowie <martin.dowie@btopenworld.com>]

Matthew Heaney wrote:
> T'Base refers to the "base range" of the type, which defines the range
> in which intermediate calculations are performed.
> 
> The standard states that the range of T'Base:
> 
> (1) includes the value 0
> (2) is symmetric about zero, with possibly an extra negative value
> (3) includes all of the values in the subtype T
> 
> So for example, if T is:
> 
>   type T is 1 .. 42;
> 
> then T'Base is
> 
>   type T'Base is -42 .. 42;
> 
[snip]
> I might have some of the details wrong, but that's the general idea.

Sorry Matt - you must be ill or something as you're a wee bit "off base" 
with your answer to this one!

Try this test prog to see what actually happens:

with Ada.Text_IO; use Ada.Text_IO;

procedure Test_Base is
    type T is range 1 .. 42;
begin
    Put_Line (T'Base'Image (T'Base'First));
    Put_Line (T'Base'Image (T'Base'Last));
end Test_Base;

It isn't -42 .. 42 but the 'First .. 'Last or the underlying integer 
representation. In this case (with ObjectAda) -2147483648 to 2147483647.

Cheers

-- Martin