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

From: Kevin Lynch (krlynch_at_[hidden])
Date: 2005-10-20 14:21:06

Deane Yang wrote:

> A general dimension/units library is, I think safe to say, useful 
> anywhere one is doing mathematical computations in a practical setting. 
> Virtually any practical mathematical calculation uses well-defined 
> dimensions and units, and such a library would help guard against 
> incorrect formulas. But I don't have specific examples (my experience is 
> just as limited as yours); I'll have to let others, if any, speak up.
> 

Here's the set of examples I bring up every time this discussion rears 
its head ...

1) Particle and nuclear physics use a "natural units" system in 
theoretical calculations where length and time have the same units, and 
energy, mass, and momentum have the same units, and the two units are 
just the inverse of each other.  You would't WANT to use SI in this 
field, because the orders of magnitude aren't even close to useful. 
Additionally, your fundamental unit is energy, which is a derived unit 
in SI.

2) Cosmology and astrophysics are in a similar situation, but use a 
different set of natural units.

3) SI doesn't include things like currency, and doesn't admit the 
possibility that unit conversions change with time.

SI is _A_ useful system of dimensions and units, but it is geared to 
physical measurements used in commerce, trade, and engineering.  It is 
not in any way a statement about mathematics, and is often the wrong 
choice for a unit system in fields of basic science.

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