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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: SPARK
Date: Sat, 15 May 2010 20:14:07 +0200
Organization: Ada At Home
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Date: 2010-05-15T20:14:07+02:00
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Another example, as much strange to me.


    procedure Limit
      (X     : in out Integer;
       Lower : in     Integer;
       Upper : in     Integer)
    --# pre    Lower < Upper;
    --# post  ((X~ < Lower) -> (X =3D Lower)) and
    --#       ((X~ > Upper) -> (X =3D Upper)) and
    --#       (X in Lower .. Upper);

    -- ....


       Limit (Local_Data, Lowest, Highest);
       Part :=3D Local_Data - Lowest;
       Whole :=3D Highest - Lowest;
       --# assert Part >=3D 0;
       --# assert Local_Data <=3D Highest;

    -- ....

The simplifier cannot prove =E2=80=9CLocal_Data <=3D Highest=E2=80=9D, a=
lthough the post  =

condition of Limit states =E2=80=9CX in Lower .. Upper=E2=80=9D so that =
it should know  =

=E2=80=9CLocal_Data in Lowest .. Highest=E2=80=9D and then =E2=80=9CLoca=
l_Data <=3D Highest=E2=80=9D.

While perhaps I'm not using it the good way (as a beginner, this may be =
a  =

possible case).

-- =

There is even better than a pragma Assert: an --# assert