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Date: Wed, 23 Nov 2011 09:50:26 +0100
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Generic-Package Elaboration Question / Possible GNAT Bug.
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Date: 2011-11-23T09:50:27+01:00
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On 23.11.11 04:49, Yannick Duchêne (Hibou57) wrote:
> Le Tue, 22 Nov 2011 16:02:06 +0100, Georg Bauhaus <rm.dash-bauhaus@futureapps.de> a écrit:
>> [1] http://www.eiffel.com/developers/design_by_contract_in_detail.html
> Oops, not good for its claims, an exemple DbC™ use case in this page is erroneous:

Care to show where the error is?

>> it will look as follows in Eiffel syntax, as part of a genericclass DICTIONARY [ELEMENT]:
>>
>> put (x: ELEMENT; key: STRING) is
>> -- Insert x so that it will be retrievable through key.
>> require
>>   count <= capacity
>>   not key.empty
>> do
>> ... Some insertion algorithm ...
>> ensure
>>   has (x)
>>   item (key) = x  count = old count + 1
>> end
> The post-condition may fails, while the pre-condition was fulfilled (unless class DICTIONARY is weird). At least, a good candidate for a legitimate exception raise :p

`put`, in DbC, may fail when it tries to establish
the state of variables so that the postcondition is
true, for example, because of a hardware error.
Can this be attributed to an incomplete precondition,
though?