Re: SI Units - has Ada missed the boat?

[kevin cline <kevin.cline@gmail.com>]

On Jul 8, 10:13 am, Martin <martin.do...@btopenworld.com> wrote:
> One of my pet hopes for Ada2005 was that it would include some method
> of automatically checking systems of units at compilation time or with
> minimal run-time checking. Alas it was voted down due to time
> pressures and technical issues (seehttp://www.ada-auth.org/ai-files/minutes/min-0403.html#AI324
> andhttp://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs/AI-00324.TXT?rev=1.3).
>
> C++ now has the Boost library (seehttp://svn.boost.org/trac/boost/browser/sandbox/units)
> with zero-runtime cost (or at least when optimisation is switched on).

A basic but usable implementation is obvious to anyone who understands
C++ template metaprogramming.  Of course a fully general
implementation is considerably more work.

>
> And now Java has a proposal for a similar beast (seehttps://jsr-275.dev.java.net/files/documents/4333/34956/jsr-275.pdf).

This is rather unwieldy since Java does not allow operator
overloading.  Who wants to read code like:

   time_aloft = sqrt(height.times(2).divide(g))

Nor can Java check the correctness of that computation at compile
time.

>
> I've been playing around with the C++ Boost library and it seems quite
> good - at least for the sort of things I would use it for (embedded
> avionics).


>
> Is anyone still working on an Ada solution to this?

A satisfactory solution seems impossible until Ada allows implicit
generic instantiation, and then it would be relatively simple.