Re: about the new Ada 2012 pre/post conditions

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

On Fri, 22 Jun 2012 18:45:16 +0200, Georg Bauhaus wrote:

> On 22.06.12 17:05, Dmitry A. Kazakov wrote:
>> On Fri, 22 Jun 2012 16:30:52 +0200, Georg Bauhaus wrote:
>> 
>>> On 22.06.12 14:43, Dmitry A. Kazakov wrote:
>>>> On Fri, 22 Jun 2012 13:54:16 +0200, Georg Bauhaus wrote:
>>>>
>>>>> On 22.06.12 09:23, Dmitry A. Kazakov wrote:
>>>>>> Neither #1 nor #2 is defendable.
>>>>>
>>>>> Maybe dynamic checking is not defendable when the attack is
>>>>> based on some biased, and, frankly, narrow set of assumptions.
>>>>
>>>> Sure, the most effective defence is just not to take any position. You
>>>> might get exposed otherwise.
>>>
>>> Who isn't taking a position?
>> 
>> You.
> 
> I don't think that #1 xor #2 can be the basis of a meaningful
> discussion of DbC, because of the frames of reference.

#1 and #2 are mutually exclusive and complete. The rest is hand waving.

>> (He was ready to debunk use of exceptions, to dismiss design of Ada I/O.
> 
> A similar comment on omitting exceptions might be circulated with Parasail,
> I think. The same Robert Dewar, lecturing at MIT, praises exceptions,
> comparing them to C's solution (checking return values all along).
> 
> Could this conviction and readiness to debunk exceptions be
> a consequence of running a particular business, the small and
> profitable niche of immensely well funded high tech?

Robert Dewar seem to consider exceptions as manifestations of contract
violations. That immediately leads to rejection of exceptions, on the
obvious basis that the contracts must be respected. The next step is, of
course, that any program raising exceptions is illegal. This is the point
where the proponents of #2 providently disconnect, because legality is to
be checked statically.

>> People could do anything in order to save dynamic checks! (:-))
> 
> Can you report the gist of the argument?

I cannot honestly summarize his argument, because as I said, there is no
way to make it. It is inconsistent.

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