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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Lost in translation (with SPARK user rules)
Date: Sun, 30 May 2010 01:03:31 +0200
Organization: Ada At Home
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Date: 2010-05-30T01:03:31+02:00
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Le Wed, 26 May 2010 12:09:17 +0200, Yannick Duch=C3=AAne (Hibou57)  =

<yannick_duchene@yahoo.fr> a =C3=A9crit:
> Lost in translation... do you know the movie ?

> No, I'm joking, this is not about this 2002 movie, that's about SPARK,=
  =

> and exactly,
> about translating some expressions in the rules language.
> [...]

In this area, the Simplifier sometimes shows slight capacities to be  =

boring.

Let a Check clause be =E2=80=9C--# check ((2 ** Count) < (2 ** 8)) -> (C=
ount < 8);=E2=80=9D
Let a user rule be =E2=80=9Cmy_rule: ((X ** Y) < (X ** Z)) -> (Y < Z)  =

may_be_deduced_from [some-obvious-conditions].=E2=80=9D

There should be an exact match, isn't it ?

Well, I guess you guess: it fails to prove the Check clause. Now, if you=
  =

would like to know why, here is: it replaces this by =E2=80=9C2 ** count=
 < 256 ->  =

count < 8=E2=80=9D, ... it turns =E2=80=9C(2 ** 8)=E2=80=9D into =E2=80=9C=
256=E2=80=9D, so that it can't see any  =

more an exact match with the user rule

I've check in the *.SLG file, this is indeed due to simplification, this=
  =

is not due to an hypothetical related error.


-- =

There is even better than a pragma Assert: a SPARK --# check.
--# check C and WhoKnowWhat and YouKnowWho;
--# assert Ada;
--  i.e. forget about previous premises which leads to conclusion
--  and start with new conclusion as premise.