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RE: The Airplane Example (was Re: StreamingXML)


streamingxml
On Tue, 2005-01-04 at 16:27 -0800, Daniela Florescu wrote:
>   I don't
> >think I can recall having *ever* had a program fail because someone
> >passed a float to a routine that expected an int.  
> 
> Really !?
> 
> For an impressive example, just take a look at this:
> 
> http://www.ima.umn.edu/~arnold/disasters/ariane.html
> 
> $7 billion dollars lost in an explosion after only a couple of seconds 
> in flight. More then 10 years of work for tens of thousands of people.
> Fortunately no human loses.
> 
> My lab at that time (INRIA) was tasked to read the millions of lines of code. 
> There were many problems found, but the cause of the explosion 
> was an unfortunate type conversion implicit in a function call if I recall
> correctly.

No.  This is an urban legend ("cubicle legend"?), which I've had trotted
out before in this argument.  I think it's a nice illustration about why
people with a strong typing mindset have a compulsion to try to express
all problems they see in terms of strong types.

The problem was a *units* conversion error, not a type conversion error.
No strongly statically typed language that I know of would have
prevented it.

It's a perfect example of the fact that most real-world bugs are caused
by value mismatches, not type mismatches.


-- 
Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Use CSS to display XML - http://www.ibm.com/developerworks/edu/x-dw-x-xmlcss-i.html
Full XML Indexes with Gnosis - http://www.xml.com/pub/a/2004/12/08/py-xml.html
Be humble, not imperial (in design) - http://www.adtmag.com/article.asp?id=10286
UBL 1.0 - http://www-106.ibm.com/developerworks/xml/library/x-think28.html
Use Universal Feed Parser to tame RSS - http://www.ibm.com/developerworks/xml/library/x-tipufp.html
Default and error handling in XSLT lookup tables - http://www.ibm.com/developerworks/xml/library/x-tiplook.html
A survey of XML standards - http://www-106.ibm.com/developerworks/xml/library/x-stand4/
The State of Python-XML in 2004 - http://www.xml.com/pub/a/2004/10/13/py-xml.html


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