* Question about 'valid
@ 2001-03-20 16:23 Peter Amey
2001-03-20 19:03 ` Mark Lundquist
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Peter Amey @ 2001-03-20 16:23 UTC (permalink / raw)
Can I ask for the collected wisdom on the following please:
Given X : T;
If X'Valid is true and X is scalar is it always true that:
X in T;
X >= T'First;
X <= T'Last;
If the answer is yes then is it still true if T is an enumeration type
with a representation clause which leads to holes in its representation.
I am currently very interested in validating aribitrary bit patterns
that arrive via memory mapped ports and want to really understand the
role of 'valid in these cases.
TIA
Peter
--
---------------------------------------------------------------------------
__ Peter Amey, Product Manager
) Praxis Critical Systems Ltd
/ 20, Manvers Street, Bath, BA1 1PX
/ 0 Tel: +44 (0)1225 466991
(_/ Fax: +44 (0)1225 469006
http://www.praxis-cs.co.uk/
--------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Question about 'valid
2001-03-20 16:23 Question about 'valid Peter Amey
@ 2001-03-20 19:03 ` Mark Lundquist
2001-03-20 19:44 ` David C. Hoos, Sr.
2001-03-29 23:56 ` Robert A Duff
2 siblings, 0 replies; 5+ messages in thread
From: Mark Lundquist @ 2001-03-20 19:03 UTC (permalink / raw)
Peter Amey <pna@praxis-cs.co.uk> wrote in message
news:3AB78417.236D1AFF@praxis-cs.co.uk...
>
> Can I ask for the collected wisdom on the following please:
>
> Given X : T;
>
> If X'Valid is true and X is scalar is it always true that:
>
> X in T;
> X >= T'First;
> X <= T'Last;
>
Yes.
> If the answer is yes then is it still true if T is an enumeration type
> with a representation clause which leads to holes in its representation.
Yes.
-- mark
P.S. Can you explain what that little ASCII graphic is in your signature
footer? I've always wondered about that! To me, it looks like a
saxophone...
:-)
> --------------------------------------------------------------------------
-
> __ Peter Amey, Product Manager
> ) Praxis Critical Systems Ltd
> / 20, Manvers Street, Bath, BA1 1PX
> / 0 Tel: +44 (0)1225 466991
> (_/ Fax: +44 (0)1225 469006
> http://www.praxis-cs.co.uk/
>
> --------------------------------------------------------------------------
%%%
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Question about 'valid
2001-03-20 16:23 Question about 'valid Peter Amey
2001-03-20 19:03 ` Mark Lundquist
@ 2001-03-20 19:44 ` David C. Hoos, Sr.
2001-03-29 23:56 ` Robert A Duff
2 siblings, 0 replies; 5+ messages in thread
From: David C. Hoos, Sr. @ 2001-03-20 19:44 UTC (permalink / raw)
"Peter Amey" <pna@praxis-cs.co.uk> wrote in message
news:3AB78417.236D1AFF@praxis-cs.co.uk...
>
> Can I ask for the collected wisdom on the following please:
>
> Given X : T;
>
> If X'Valid is true and X is scalar is it always true that:
'Valid is defined ONLY for Scalar types.
>
> X in T;
> X >= T'First;
> X <= T'Last;
Yes
>
> If the answer is yes then is it still true if T is an enumeration type
> with a representation clause which leads to holes in its representation.
Yes.
>
> I am currently very interested in validating aribitrary bit patterns
> that arrive via memory mapped ports and want to really understand the
> role of 'valid in these cases.
>
> TIA
>
> Peter
>
> --
> --------------------------------------------------------------------------
-
> __ Peter Amey, Product Manager
> ) Praxis Critical Systems Ltd
> / 20, Manvers Street, Bath, BA1 1PX
> / 0 Tel: +44 (0)1225 466991
> (_/ Fax: +44 (0)1225 469006
> http://www.praxis-cs.co.uk/
>
> --------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Question about 'valid
2001-03-20 16:23 Question about 'valid Peter Amey
2001-03-20 19:03 ` Mark Lundquist
2001-03-20 19:44 ` David C. Hoos, Sr.
@ 2001-03-29 23:56 ` Robert A Duff
2001-03-30 3:41 ` Ken Garlington
2 siblings, 1 reply; 5+ messages in thread
From: Robert A Duff @ 2001-03-29 23:56 UTC (permalink / raw)
Peter Amey <pna@praxis-cs.co.uk> writes:
> Given X : T;
>
> If X'Valid is true and X is scalar is it always true that:
>
> X in T;
> X >= T'First;
> X <= T'Last;
Yes.
> If the answer is yes then is it still true if T is an enumeration type
> with a representation clause which leads to holes in its representation.
Yes. But I would be a little bit wary of compiler bugs in that area.
> I am currently very interested in validating aribitrary bit patterns
> that arrive via memory mapped ports and want to really understand the
> role of 'valid in these cases.
I would avoid hole-y enums for this purpose, and just use integer types
that happen to have no extra values (eg "mod 2**32" or whatever).
- Bob
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Question about 'valid
2001-03-29 23:56 ` Robert A Duff
@ 2001-03-30 3:41 ` Ken Garlington
0 siblings, 0 replies; 5+ messages in thread
From: Ken Garlington @ 2001-03-30 3:41 UTC (permalink / raw)
"Robert A Duff" <bobduff@world.std.com> wrote in message
news:wcclmpo86yd.fsf@world.std.com...
: Peter Amey <pna@praxis-cs.co.uk> writes:
: > I am currently very interested in validating aribitrary bit patterns
: > that arrive via memory mapped ports and want to really understand the
: > role of 'valid in these cases.
:
: I would avoid hole-y enums for this purpose, and just use integer types
: that happen to have no extra values (eg "mod 2**32" or whatever).
Oh, I hope not. I was a big supporter of 'Valid precisely because we always
had to do such annoying workarounds in Ada83...
^ permalink raw reply [flat|nested] 5+ messages in thread
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2001-03-20 16:23 Question about 'valid Peter Amey
2001-03-20 19:03 ` Mark Lundquist
2001-03-20 19:44 ` David C. Hoos, Sr.
2001-03-29 23:56 ` Robert A Duff
2001-03-30 3:41 ` Ken Garlington
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