[boost] Re: Physical Quantities revisited

From: Andy Little (andy_at_[hidden])
Date: 2003-10-23 09:38:40

"Ross MacGregor" <ross__macgregor_at_[hidden]> wrote in message
news:bn89jt$1ta$1_at_sea.gmane.org...
> For example if you want your basic unit of length to be 299,792,458
> meters and you wanted your calculations to use floats. You may want to
> specify it like this:
>
> si_unit<float, 2.99792458e+8, meter_t> light_meters;

Slight problem on the Float here !
How does it work with (say) force?

> si_unit<long double, 1.0, meter_t> meters;
>
> light_meters x_lm = 2500;

Assume this means  2500 light_meters rather than 2500 meters .?

> light_meters y_lm = 10;
> light_meters z_lm = x_lm + y_lm;
>
> meters m = lm; // warning possible loss of precision
>
> We are essentially creating a custom floating point value, but only
> incurring the overhead during unit conversion.

Critical issue is whether the internal value of light_meters is 1  or
2.9979245e8 ?
(I would argue on 1)
But basically Yup! :-)

regards
Andy little