Re: [boost] Quantity library: any interest?

From: renej_at_[hidden]
Date: 2003-04-27 11:15:05

>>From: <renej_at_[hidden]>
>
>> we use the int-based template approach for a couple of years now in
>> our AGV controller software. We actually sometimes reach the stage
>> that it works when succesfully compiled and linked. Since our control
>> software is physics throughout (field of robotics), the type safety is
>> very important. However, besides the basic SI units we also have
>> 'angle' as a dimension which allows us to distinguish 'velocity' and
>> 'angular velocity' for example. Hence, from out 'real user' experience
>> (engineering point of view) it would be a necessity to add 'angle' as
>> a dimension without breaking already defined quantities. Most (all?)
>> units libraries already define 'angle' to be dimensionless, which is
>> true in
>> scientifically spoken, but pragmatically (engineering ;-) less handy.
>
> There's another question. If we add angle as a dimension, then what
> kind of angle is it? There are several kinds of angles, such as radians
> (plane angle) and steradians (solid angle). If both were represented by
> the same angle dimension, then it probably wouldn't make much sense to
> add radians and steradians (and what would be the resulting quantity?),
> yet, the library would allow it.

in our implementation (plane) angle is sufficient, so we don't bother
with solid angle for the moment. However, I think it should have it's
own dimension since steradian != radian^2 (although m^2/m^2 = (m/m)^2 ;-)

but I think a unit library would reach a much broader audience if it allows
to choose what dimensions are handled and how. For my application field
it is necessary to incorporate everything related to robotics (time,
length, angle, charge, mass), but temp, luminious intensity, amount of
substance not really. I think it would be nice to be able to select only
those you need in a unit lib and add your own "dimensions" if needed

renej

>
>
> Regards,
>
> Terje
>
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