Re: Announce: Grace project site operational

[Darren New <dnew@san.rr.com>]

Hyman Rosen wrote:
> 
> Darren New wrote:
> > Can someone explain why a combinatoric explosion of types is bad
> 
> Several reasons. First of all, someone has to write them. Second,
> the set of possible units is infinite, so declaring all of the
> types and operations is impossible; you can only declare the
> subset that you think anyone will ever need, and if you're wrong,
> the extra ones will have to be done by the users. Third, it feels
> inelegant to have to do this - in the real world, units systems
> such as SI consist only of a small number of fundamental units
> and all the rest are composed of those. One would hope that this
> could be captured by the programming.

Well, it does just seem to me pretty trivial to write a program that
takes something like

=distance
=time
velocity=distance/time
area=distance*distance
volume=distance*distance*distance

and turn such a file into the appropriate set of Ada type and function
declarations, whether it's 50 lines or 5000 lines, that when "with"ed
and "used" could make for safe unit conversions. You need another unit?
Add it to the file and regenerate the Ada. I mean, basically, isn't this
what the C++ compiler is doing with the templates, except only creating
those combinations you use?

Of course, it could be made much more sophisticated too. 

Or don't Ada people do things like that? :-)

-- 
Darren New 
San Diego, CA, USA (PST). Cryptokeys on demand.
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