Re: [boost] Re: Re: Re: Re: quantity libraries

From: Anatoli Tubman (anatoli_at_[hidden])
Date: 2001-09-04 01:37:39

On Monday 03 September 2001 20:21, Paul Bristow wrote:
> The main potential problem is the astronomers, but even a megaparasec is
> only
> about 3 million light years  where a light year is about 10^15 meter, the
> base unit.
>
> So even with float with a max of 10^38 there is quiet a bit of headroom,
> and with double 10^308 there is plenty.

Actually, the main problem is the physicists. You can't store e^2 or h^2
or Planck time expressed in SI units in a float.

See http://physics.nist.gov/cuu/Constants/ for more info.

I don't know squat about superstrings, but I've heared they are either
10- or 26-dimensional. It is conceivable that, say, Planck length to the
power of 10 or 26 is needed, or will be needed in the future. For such
exponents even double is too small.

There's an additional benefit of a system where interesting fundamental
constants have value of 1: you can optimize out multiplications by
them.

> [...] If templating can allow other base systems without cost, then OK

Sure templating can do it. I've done it in a prototype library.

-- 
anatoli at ptc dot com -- opinions are mine