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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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Newsgroups: comp.lang.ada
Subject: Re: SPARK : third example for Roesetta - reviewers welcome
Date: Sun, 15 Aug 2010 22:07:44 +0200
Organization: Ada At Home
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Date: 2010-08-15T22:07:44+02:00
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Le Sun, 15 Aug 2010 20:42:27 +0200, Phil Thornley  =

<phil.jpthornley@gmail.com> a =C3=A9crit:
> in http://www.sparksure.com/resources/Rosetta_Binary_Search.txt


> else
>    -- Switch to lower half subrange.
>    Upper :=3D Position - 1;
>    Position :=3D (Lower + Upper) / 2; -- <<<
> end if;
>-- [...]
>else
>    -- For "Middle <=3D Upper" in loop assertion.
>    -- Switch to upper half subrange.
>    Lower :=3D Position + 1;
>    Position :=3D (Lower + Upper) / 2; -- <<<
> end if;

Interesting to note: you moved =E2=80=9CPosition :=3D (Lower + Upper) / =
2;=E2=80=9D inside  =

logical branch, I suppose to ease prove, as the instruction is right in =
a  =

context which makes its validity more obvious. This is indeed better tha=
n  =

the idea of the factorization I used.

This topic makes me think about the latter about the Middle variable  =

turned into a direct use of Position. May be I did "automatic useless  =

optimization" here.

That is funny, because it happens I do the same (that is why I suppose I=
  =

was not so good here due to a kind of "inappropriate automation").