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From: Spiros Bousbouras <spibou@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Contracts in generic formal subprogram
Date: Wed, 12 Apr 2023 02:18:45 -0000 (UTC)
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On Tue, 11 Apr 2023 14:03:27 +0200
"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote:
> The formal meaning of weaker/stronger relation on predicates P and Q:
> 
> weaker   P => Q
> stronger Q => P
> 
> The formal rationale is that if you have a proof
> 
>    P1 => P2 => P3
> 
> Then weakening P1 to P1' => P1 and strengthening P3 => P3' keeps it:
> 
>    P1' => P2 => P3'

You have it backwards ; if  P1'  implies  P1  then  P1'  is stronger
than  P1 .