Re: [boost] Re: A Physical Quantity library for boost?

From: boost (boost_at_[hidden])
Date: 2001-06-26 01:50:13

Salut,

On Tuesday 26 June 2001 04:25, you wrote:

> I.e. if you can cancel dimensions by
>
> 	sin ( x / L ) * metres
>
> why shouldn't you have to do that for multiply too:
>
> 	(x / L) (y/L) * metres(2)
>

because you can factor out the dimensions in the multiplication example,
and you can't with the sine.

The general rule is, that the result must not depend on the unit choosen,
it shouldn't matter if you use inch or meter, the end result has to be the 
same. That's not true for the sine example, but it is in the second.

> > are properly handling your physics equations, it should never (strictly
> > speaking) be necessary.  It is kindof like casting away const - sure,
> > you really really need to sometimes, but most of the time it is
> > indicative of an error on your part to need to do so.

I never had to cast away units, sometime one redefine c = \hbar = 1 
to get rid of all notation inconveniences, but that's just another unit 
system.

Best wishes,
Peter