Re: Ada Interfaces and the Liskov Substitution Principle

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Fri, 01 Jun 2007 13:41:11 +0200, Georg Bauhaus wrote:

> Dmitry A. Kazakov wrote:
>> On Thu, 31 May 2007 13:44:40 +0200, Georg Bauhaus wrote:
>> 
>>>  When they write,
>>>   a := a + 1;
>>> the may not be thinking about a commutative group of integers,
>> 
>> It is no matter what they think, it matters what they write.
> 
> This seems a contradiction to what you say below, about basing
> solutions on technology/science.

Why? This basing is about an ability to communicate the solution = using
some formalism (like one of mathematics).

> OTOH, when we started from LSP as a design principle, we started
> from a guiding principle, I think.

Which indicates the actual problem...

> This means programmers who
> do not accidentally write following the principle. So what are
> the principles they have actually been following when
> producing a solution that works even though the math behind it
> is not known/mainstream/acceptable?

LSP as a vague principle is just useless and confusing. It results in
countless silly discussions about Circles and Ellipses. Similarly, one
could discuss designs of a perpetual-motion machine. A minimal formalism
would immediately clarify it.

>>>> No, the point is that they cannot be mapped (implemented), this is why
>>>> mathematics is necessary to describe what is going on, because no machine
>>>> would be sufficient for that.
>>> But what is actually going on in /dev/random?
>> 
>> Realization of a random variable.
> 
> What is realization in a machine if not an implementation?

Implementation of a realization is a number (stored/computed). Note the
difference between a number and a random variable, hence the
implementations of.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de