Re: Ariane-5: can you clarify? (Re: Please do not start a language war)

[Karel Th�nissen <thoenissen@hello.nl>]

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Nick Leaton wrote:
> 
> Karel Th�nissen wrote:
> 
> > THERE COULD NOT POSSIBLY HAVE BEEN A ROLE FOR ASSERTIONS ON-FLIGHT

> If I generalise what you say, running production code with assertions
> will not make a difference. However, there are things you can do. If
> there
> was an exception handler built, then it can make choices. In the Ariane
> case,
> an exception from the SRI post launch can be ignored. If you were
> writting
> a system that involved file handling then it could, perhaps try
> something
> to make a file handle or space available. For example, prompt the user
> to empty a trash can.

True, I am sorry, let me clarify this a bit more. I fully agree that
exception handling in production code is in general very valuable (and
often the only reasonble way to go), and the examples you gave point out
this fine. And indeed in the case of the SRI system, the exception could
have been confined to the allignment software, as it was superfluous at
that point. But what if it was not in superfluous subsystem? You cannot
shut down the module that calculates the flight data. This bug could
have creeped in there just as well, because testing for both subsystems
was as strict. Or what about a file system that prompts for human
interaction in a overnight batch run? Sometimes there are no
possibilities for recovery. And IMHO this conversion problem is an
example of just that. But very likely there are a lot of exceptions
handlers in this SRI software which do their work as intended and that
could not be left out.

> From personal experience I have found this to be the case. Being able to
> test your comments is very useful!
>  
> Nick

I fully agree, and every one should do this. But do you get this taught
in software engineering class or do software engineering methods or
languages enforce this? Do project managers require this?
To further clarify my/our point. Right now tens of thousands of
programmers wish that assumptions were more accurately documented in the
code - on the spot - if only by means of informal comments. These
programmers are making our software ready for the Y2000, they know the
assumptions made, if only they could easily find those spots.