Re: Another Idea for Ada 20XX

[Wilhelm Spickermann <wilhelm.spickermann@t-online.de>]

--On Sunday, December 02, 2001 18:49:24 -0500 Patrick Hohmeyer 
<pi3_1415926536@yahoo.ca> wrote:

> Interesting approach, but at first glance I dont see how
> you'll solve the Celsius = Kelvin + 273.15 problem.
>
> This solution seams only to work with units where zero in one
> unit equals zero in the other as well.

This problem is not a programming problem -- and it has been 
solved already.

Units in physics may not carry any offset information as they 
are not capable to do this. Doing it would destroy the 
fundamental concept of equality being a replacement permission: 
"The outside temperature is 10 degrees celsius, that´s 10 
degrees celsius less than the temperature of my room.". If 10 
Degrees Celsius would be equal to 283.15 Kelvin, it would have 
to be possible to replace *both* occurences. Giving: "The 
outside temperature is 283.15 Kelvin, that´s 283.15 Kelvin less 
than the temperature of my room." Wow, too hot for me.

The solution is (IFAIR it´s from the International Conference on 
Measurements and Units... in 1972): "The temperature is 10 
Degrees Celsius" is just a lax abbreviation for: "The 
celsiustemperature is 10 Kelvin". So it´s a different physical 
value with the same unit and not the same physical value with a 
different unit. Note that the conversion between celsius 
temperature and absolute temperature can now be expressed in a 
simple equation: TC = TA + 273.15 K

The same holds for pseudo units like the old german "atü" (car 
tires) and "Vss"(TV electronics).

So it´s not a problem of unit conversion, but a problem occuring 
in the user interface, where you will have to deal with pseudo 
units.

Wilhelm