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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: SPARK : third example for Roesetta - reviewers welcome
Date: Sun, 15 Aug 2010 21:57:52 +0200
Organization: Ada At Home
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Date: 2010-08-15T21:57:52+02:00
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Le Sun, 15 Aug 2010 20:42:27 +0200, Phil Thornley  =

<phil.jpthornley@gmail.com> a =C3=A9crit:
> I decided that it would more interesting to strengthen the post-
> condition to say that 'not Success' means that no element in Source is=

> equal to Item.

After I have read this, it is more clear :


>    --# post (Found -> (Source (Position) =3D Item)) and
>    --#      (not Found ->
>    --#         (for all I in Index_Type range Source'First .. Source'L=
ast
>    --#                                  =3D> (Source(I) /=3D Item)));

This is indeed a more strong/strengthened postcondition than mine. To ta=
lk  =

with a word I like : this is more expressive.


>    --# assert not Terminated and
>    --#        Lower >=3D Source'First and
>    --#        Upper <=3D Source'Last and
>    --#        Position >=3D Lower and
>    --#        Position <=3D Upper and
>    --#        not Found and
>    --#        (Lower > Source'First -> Source(Lower - 1) < Item) and
>    --#        (Upper < Source'Last -> Source(Upper + 1) > Item);

Interesting to study: you could move all in the loop assertion.


(I am still going on with reading)