"Strong typing vs. strong testing"

[Niklas Holsti]

Albert van der Horst wrote:
> In article <87fwwvrnmf.fsf at kuiper.lan.informatimago.com>,
...
>> I would even go further.
>>
>> Types are only part of the story.  You may distinguish between integers
>> and floating points, fine.  But what about distinguishing between
>> floating points representing lengths and floating points representing
>> volumes?  Worse, what about distinguishing and converting floating
>> points representing lengths expressed in feets and floating points
>> representing lengths expressed in meters.
> 
> When I was at Shell (late eighties) there were people claiming
> to have done exactly that, statically, in ADA.

It is cumbersome to do it statically, in the current Ada standard. Doing 
it by run-time checks in overloaded operators is easier, but of course 
has some run-time overhead. There are proposals to extend Ada a bit to 
make a static check of physical units ("dimensions") simpler. See 
http://www.ada-auth.org/cgi-bin/cvsweb.cgi/acs/ac-00184.txt?rev=1.3&raw=Y 
and inparticular the part where Edmond Schonberg explains a suggestion 
for the GNAT Ada compiler.

> A mission failure is a failure of management. The Ariadne crash was.

Just a nit, the launcher is named "Ariane".

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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