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From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Copy vector in Ada
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Date: 2012-11-07T13:03:07+01:00
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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.

Why? Because the workplace is governed by rules that language
theory/ideology/religion/principles will not normally cover.

A similar example will explain why principles like a theoretically
clean notion may turn out to be pointless, even a hindrance once
they are used outside the clean room:

Sometimes programs would modify themselves in a perfectly,
provably safe way, leading to sufficient performance in
terms of time and storage. And no matter what one might have
to say about their design, only by violating today's principles
could they achieve their stated goals. Today, it may not even
be possible to run such programs, because modifications are
detected, and the program is stopped. Principles have changed.

But are these self-modifying programs not "programs" anymore
because they were "improperly named `programs'"?

Similarly, I'll say that "inheritance" without further adjectives
is just insufficiently defined, and void of purpose (for the
workplace). And any single definition cannot name the "right"
inheritance.

So we have
 "Thou shalt follow the substitution principle!"
and
 "today's orthodoxy of language theory".

(Well, actually, the 1980s' theory, or even earlier.)

That said, I wish there was more software whose designers had
followed the substitution principle, and not reused hash tables
as parents, say. (Even when that's practical if you have the
source.)