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Date: Wed, 12 May 2010 20:15:55 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: GNAT packages in Linux distributions
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Date: 2010-05-12T20:15:55+02:00
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On 12.05.10 19:24, Dmitry A. Kazakov wrote:
> On Wed, 12 May 2010 18:06:16 +0200, Yannick Duchêne (Hibou57) wrote:
> 
>> Well, I've noted you do not like runtime-check because it is not [formal]  
>> proof of anything, but no one said it is formal proof, this is just better  
>> to catch error the sooner and understand why this was an error.
> 
> Yes, it is better but that is not the point. Which is there is no
> substantial difference between Eiffel precondition and C's if statement
> beyond syntax sugar, and that if-statement is less misleading. 

Another important difference between a simple "if" and DbC assertions:
The routine conditions must be consistent along the inheritance chain.
It seems silly to have the programmer walk up and down the chain and
make sure that substitutability isn't violated by manual "if" style
preconditions.
Hence, Eiffel's

  require else

and

  ensure then

for overriding routines.