From: Brian Drummond <brian_drummond@btconnect.com>
Subject: Re: SPARK again : for-loop vs single loop - a strange case
Date: Thu, 27 May 2010 22:50:06 +0100
Date: 2010-05-27T22:50:06+01:00 [thread overview]
Message-ID: <40qtv5pfcsomupgedmd5iait1bnbtmdlg8@4ax.com> (raw)
In-Reply-To: op.vddp3fvvxmjfy8@garhos
On Thu, 27 May 2010 21:36:41 +0200, Yannick Duch�ne (Hibou57)
<yannick_duchene@yahoo.fr> wrote:
>Hi all,
>
>This will require some further investigation on my own side, however, I
>would like to open a topic about it, if ever someone wants to share about
>the same matter.
>
>I was proving something built around a for-loop. Every thing was going,
>when I've meet a trouble and decided to switch to a classic loop and an
>exit statement and a local variable.
>
>There was a Check clause in the for-loop, which was looking like this:
>
> for L in T range 1 .. N loop
> ...
> --# assert ...;
> ...
> --# check (2 ** (T'Pos (L) + 1)) = ((2 ** T'Pos (L)) * 2);
> ...
> end loop;
>
>
>This Check clause was proved by the Simplifier without any trouble.
>
>I then switch to a class loop, looking like this:
>
>
> L := 1;
>
> loop
> ...
> --# assert ...;
> ...
> --# check (2 ** (T'Pos (L) + 1)) = ((2 ** T'Pos (L)) * 2);
> exit when L = Length;
> L := L + 1;
> ...
> end loop;
>
>Then, the Simplifier was not able anymore to prove this Check. I don't
>understand, as this Check should only depends on a basic rule, a rule by
>definition. So why the same rule is not applied when I use a classic loop
>instead of a for-loop ?
Is it relevant here that the range of L is known in the first loop, and
can (presumably) be shown to be less than T'Size?
Perhaps L in the second example can be declared of a subtype with
appropriate range? (If it already is, that wasn't shown in the posted
code)
- Brian
next prev parent reply other threads:[~2010-05-27 21:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-27 19:36 SPARK again : for-loop vs single loop - a strange case Yannick Duchêne (Hibou57)
2010-05-27 21:50 ` Brian Drummond [this message]
2010-05-27 23:21 ` Yannick Duchêne (Hibou57)
2010-05-28 8:14 ` Phil Thornley
2010-05-28 9:00 ` Yannick Duchêne (Hibou57)
2010-05-28 11:50 ` Phil Thornley
2010-05-28 15:13 ` Phil Thornley
2010-05-28 22:46 ` Yannick Duchêne (Hibou57)
2010-05-28 22:41 ` Yannick Duchêne (Hibou57)
2010-05-28 9:04 ` Yannick Duchêne (Hibou57)
2010-05-28 12:17 ` stefan-lucks
2010-05-28 22:52 ` Yannick Duchêne (Hibou57)
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