Re: Ada83/95 Compatibility

["Jeffrey R. Carter" <spam@spam.com>]

jeff@thecreems.com wrote:

>  type My_Big_Int is range -2**31 .. 2**31 -1 ;
>  for My_Big_Int'size use 32;
> 
>  subtype little_range is My_Big_Int range 0 .. 255;
> 
>  A : My_Big_Int;
>  B : Little_Range;
> 
> I was not surprised that Little_Range'size = 8
> 
> What surprised me was that b'size comes back as 8. I've re-read the
> representation chapter again and I think the compiler is probably
> within its rights to do this.

This seems correct to me. A value of subtype Little_Range can be stored in 8 
bits (hence its 'Size is 8). What's important is that operations on values of 
Little_Range are done using My_Big_Int'Base.

If you need to store a value in 32 bits (for interfacing to HW, for example) but 
be sure it's in Little_Range, you can always specify the 'Size of the object:

X : Little_Range;
for X'Size use My_Big_Int'Size;

-- 
Jeff Carter
"I soiled my armor, I was so scared."
Monty Python & the Holy Grail
71