Re: [boost] Interest in dimension/unit-checking library?

From: Matt Calabrese (rivorus_at_[hidden])
Date: 2005-10-27 11:18:22

On 10/27/05, Daryle Walker <darylew_at_[hidden]> wrote:

> You have to use an absolute scale, like
> Kelvin[1]. Back when thermometers were invented, no one knew enough
> thermodynamics to realize the existence of an absolute zero, let alone
> have
> any technology that can generate temperatures close to that point.

It doesn't matter that Kelvin is based around 0. The concept of points,
vectors, and scalars still exists, just like they do for lengths, which are
usually based around 0, as well as any other unit type. You can have length
points too, and in fact those are extremely common as well (length points
are points in space, which are used all of the time). Just because Kelvin,
like most lengths, is based around 0, does not change that fact. It still
does not mean that it makes sense to add the temperature at the beginning of
the day with the temperature at the end of the day whether it's kelvin,
celsius, or otherwise. You still have the the distinct concepts of points
(absolute locations), vectors (translations), and scalars (magnitudes). A
celsius vector is convertible to a Kelvin vector. A fahrenheit point is
convertible to a Kelvin point. The logical difference is always there, just
like with lengths and all other units. You are just confused since usually
you don't usually explicitly state "vector", "point", or "scalar". If you
find this hard to understand, you can often get away with just always using
scalars, but in many cases this will cause you problems (such as with
temperatures).

--
-Matt Calabrese