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Date: Wed, 07 Nov 2012 19:06:11 +0100
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Copy vector in Ada
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Date: 2012-11-07T19:06:10+01:00
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On 07.11.12 17:11, Yannick Duchêne (Hibou57) wrote:
> Le Wed, 07 Nov 2012 13:03:08 +0100, Georg Bauhaus
> <rm.dash-bauhaus@futureapps.de> a écrit:
> 
>> On 06.11.12 20:47, Yannick Duchêne (Hibou57) wrote:
>>> Now, talking about proper naming of things, how would you explain to a
>>> student, that sometime “type” must follow the substitution principle, and
>>> sometime, it do exactly the opposite?
>>
>> The challenge is to explain why the substitution principle is
>> a valid commandment: A valuable piece of formal theory, it may
>> not offer sufficient justification in the workplace.
> 
> It was never promoted as a commandment in my comments, but said it is not to
> be confused to something else, and to be followed when expected, and not
> followed when not applicable (like not using it in place of reuse, because
> this always gives the illusion of one thing and give another instead). This
> find as much justifications as predictability do.
> 
>> Why? Because the workplace is governed by rules that language
>> theory/ideology/religion/principles will not normally cover.
> 
> No religion/ideology was spread, but some basic principle recalled.


Well, a basic principle about derived types was stated,

 "a derived type has to cover a base type, and will probably
 do more, but in anyway, not less",

The commandment can be called a basic principle in the light of
the substitution principle, but not necessarily in the light of
correct algorithms at workplace. To show the absence of issues might
be more work. However, if this work makes your algorithm work within
specs, the basic principle is at odds with workplace requirements.