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From: brian@comp.vuw.ac.nz (Brian Boutel)
Newsgroups: comp.lang.misc
Subject: Re: Run-time Type Errors in Smalltalk
Message-ID: <1991Apr15.234559.16293@comp.vuw.ac.nz>
Date: 15 Apr 91 23:45:59 GMT
References: <1917@optima.cs.arizona.edu>
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In article <1917@optima.cs.arizona.edu>, gudeman@cs.arizona.edu (David
Gudeman) writes:
|> In article  <1991Apr15.065146.16680@tkou02.enet.dec.com> Norman
|> Diamond writes:
|> ]In article <4243.2805b94a@iccgcc.decnet.ab.com>
|> klimas@iccgcc.decnet.ab.com writes:
|> ]>	Some info that I picked up from a company doing a lot of big
|> ]>	project work with C++ (i.e. strong type checking language) was
|> ]>	that postmortems on their project revealed only 10% of their
|> ]>	errors were captured by strong type checking.
|> ]...
|> ]In any other field of engineering, a 10% increase in safety would
|> always
|> ]be applied.  To reject it would be grounds for lawsuits, at least.
|> 
|> How do you get a 10% increase in safety from the above?  If they
|> hadn't caught those errors by static typing they would have caught
|> them by testing -- the same way the found the other 90% of the
|> errors.
|> This logic error combined with the strident tone of the article
|> suggests that your convictions are affecting your thinking.
|> --

The claim that testing catches all errors is laughable. Errors show up
in production code every day. Testing, as we tell first year students,
does not demonstrate the absence of errors, only their presence.

The figures quoted refer only to errors that have been detected, not to
all errors.

So what can be said about all the errors in the quoted C++ project that
were not caught by testing and are still in the production code? 

I'll tell you. They are not type errors.

--brian

 
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