Re: Rep-spec question

[Nick Roberts <nickroberts@callnetuk.com>]

Keith Thompson wrote:
> ...
> I think there's an AI that modifies the above advice.
> ...

It's AI95-00051/08 (98-04-01), which is binding. I won't quote the
entire thing wholesale, but in the middle it says:

-----

3. For a non-aliased object, the implementation should support a Size
clause specifying a Size up to (at least) the following values, which
depends on the class of the object.  (Similarly, the implementation
should support a Component_Size clause and a
record_representation_clause specifying the Size of a component up to
(at least) these values, depending on the class of the component.)

    - For a signed integer, up to the Size of the largest signed integer
      type supported by the implementation.

    - For a modular integer, up to the Size of the largest modular
      type supported by the implementation.

    - For an object of an enumerated type, up to the Size of the largest
      signed integer type, or the largest modular type, whichever is
      smaller.

For fixed point, floating point, access, and composite objects, the
implementation need not support any Size other than what would be chosen
by default.

In the discrete case, any extra bits are set to appropriate values when
assigning to the object whose Size has been specified; for example, the
value being assigned should be zero-extended or sign-extended as
appropriate.  When reading from the object, any extra bits may be
ignored.

-----

Which I think more or less clarifies the question.

-- 
Nick Roberts
Computer Consultant (UK)
http://www.callnetuk.com/home/nickroberts
http://www.adapower.com/lab/adaos