[boost] Re: Units libraries.,.. (long reply)

From: Deane Yang (deane_yang_at_[hidden])
Date: 2004-01-13 23:18:59

Andy Little wrote:
> "Dave Gomboc" <dave_at_[hidden]> wrote
>>Is there an intent for any of these proposed dimensional and unit
>>libraries to restrict the types of operations being performed according to
>>the scale of measurement that the unit belongs to?  e.g. 10 kelvins / 5
>>kelvins gives 2 kelvins, but 10 degrees Celsius / 5 degrees Celsius gives
>>not only 2 degrees Celsius but also a compiler warning? :-)  (An error
>>would be too severe -- it's pretty common for social scientists to take
>>means of ordinal data.)
> 

As I've mentioned before, one simply needs to distinguish between
absolute temperature measurements (even in kelvins) and
relative temperature measurements (representing the difference between
two absolute temperatures).

Why even in kelvins? Two reasons:
1) For temperature differences, degrees Celsius should be regarded
as being identical to degrees Kelvin
2) Temperature differences in degrees Kelvin are allowed to be negative.
Absolute temperature in degrees Kelvin is not.