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From: =?iso-8859-15?Q?Yannick_Duch=EAne_=28Hibou57=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: SPARK : surprising failure with implication
Date: Wed, 02 Jun 2010 09:56:23 +0200
Organization: Ada At Home
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Date: 2010-06-02T09:56:23+02:00
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Le Wed, 02 Jun 2010 09:42:58 +0200, Dmitry A. Kazakov  =

<mailbox@dmitry-kazakov.de> a =E9crit:

> (forall A,B in Boolean)
>
> not B =3D> not A =3D
>    =3D not not B or not A =3D
>    =3D B or not A =3D
>    =3D not A or B =3D
>    =3D A =3D> B
>
Yes, you confirmed that is right and so I'm not silly. But why Simplifie=
r  =

do not seems to know it ? It is the basis of inference logic. That is wh=
y  =

I have such a weighty question in my mind : I wonder if I did something =
 =

wrong somewhere or if something is broken.

Do you have an idea ?

-- =

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.