Re: [boost] Re: Re: quantity libraries

From: Ken Shaw (ken_at_[hidden])
Date: 2001-08-30 11:41:57

----- Original Message -----
From: "Anatoli Tubman" <anatoli_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Thursday, August 30, 2001 11:03 AM
Subject: Re: [boost] Re: Re: quantity libraries

> On Thursday 30 August 2001 17:25, Burkhard Kloss wrote:
> > [me:]
> > >Oh come on. The question is not what is more fundamental, but what is
> > >more useful. Which makes it much trickier, because usefulness is
> > >relative. Meter is also a derived unit. This does not make it
> > >any less useful.
> >
> > Well, meters are useful to a larger population - i.e. the rest of the
world
> > outside of the US and UK.  Also, technical people in non-metric
countries
> > will understand metric units because they are also in use; people from
> > metric countries generally have no idea what feet etc are.
> >
>
>
> A lot of fine technical people understand joules, but *use*
electron-volts.
>
> I mean,
>  (1) different users want to use different measurement-systems, and
>  (2) we can build a library that supports *any* kind of measurement-system
>      *at no additional cost to the user.*
>
> Adding (1) and (2) together, I cannot see in what respect a SI-only
library
> would be better.
>

Simple first reason, what is the conversion of kilograms to pounds? 2.2
pounds to the kilogram right? WRONG! There is no conversion between the two,
kilograms measure mass ( a constant ) and pounds measure weight  ( a
relative measure of mass * gravity ). If the quantity library allows both
systems some compiler manufacturer will implement that wrong conversion and
it will inevitably sneek into some calculation where it does matter.

Ken Shaw