Re: Papers on the Ariane-5 crash and Design by Contract

[jezequel@irisa.fr (Jean-Marc Jezequel)]

In article <milkweed-1803970737590001@port3.chester.smallmedia.com>, milkweed@plainfield.bypass.com (Anders Pytte) writes:
>In article <tz8g1xtzx9y.fsf@aimnet.com>, nouser@nohost.nodomain (Thomas) wrote:

>I concur. In earlier threads I pushed the point that choice of language is
>not as significant as good coding practices. Meyers et. al. are to be

True.

>congratulated on creating a language that incorporates as much good coding
>practices as may be possible into a language. But they lose credibility by
>asserting that language can enforce good coding practices.

The language by itself does not (and cannot) enforce good coding practices.
You can do Fortran in Eiffel or in Ada. I wonder who is asserting the contrary:
I do not for one, and I do not remember B. Meyer "asserting that language can 
enforce good coding practices". What is true, IMHO, is that languages differ
by the level of integration/support of best OO practices, and thus make it more
or less easy for programmer to adopt them.
You say yourself that Eiffel is "a language that incorporates as much good coding
practices as may be possible into a language".  For myself, I wouldn't even
go that far.


>I have learned to use assertion exhaustively in C++, even though I do not
>work on critical products. I get the point about auto-extraction of
>assertions into documentation, but in the end most coders feel more secure
>looking at code itself (documentation may be incomplete or out of date).
>There is no substitute for self documenting code, and for that purpose
>assertion is priceless.

It seems that we are actually in agreement.

>I expect Meyers to push his own products, but to imply the Ariane-5 crash
>was caused by poor choice of programming language seems out of step with
>his otherwise impeccable manners.

Unless our English is so bad that it betrays our thinking, we 
*never* implied such a thing. Just a point in a case: Eiffel simply did not exist when they 
worked on Ariane4. Let me quote the relevant section of the paper:

<<Is it the programming language's fault?
Although one may criticize the Ada exception mechanism, it could have been used here
 to catch the exception. In fact, quoting the report: [omitted]
In other words the potential problem of failed arithmetic conversions was recognized.
 Unfortunately, the fatal exception was among the three that were not monitored,
 not the four that were.>>

In case it is not clear enough, I repeat again: *it is not a language problem*
Let me quote another part of the paper:
<<Does this mean that the crash would automatically have been avoided had the mission used
a language and method supporting built-in assertions and Design by Contract? >>

Please note the "language and method supporting built-in assertions and Design by Contract"
and please do not reduce it to : "a language". 



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