[boost] Re: Re: Re: Re: Re: Physical quantities

From: Andy Little (andy_at_[hidden])
Date: 2004-01-17 03:58:34

"Kevin Lynch" <krlynch_at_[hidden]> wrote

[snip]

> If we had a good, flexible DA+unit system for me, I could use it to
> define the time unit in terms of taus instead of seconds, and use the
> equation in its original form, and still get the aesthetic and technical
> benefits without teh work of non-dimensionalization.  But, doing so
> would require flexibility in the definition of unit systems.

I will certainly bear that in mind for my next version. Of course it is
perfectly possible to use the current libs (pqs,Yanl,yapqul) and others in
the file section with your own set of dimensions.  the code for each
dimension can represent anything you like. (pqs-1-00-01 limits you to 7
dimensions, I will look into how much work is required by a user if se
requires a larger 'set of dimensions'. I think this is not as much as might
be expected [using mpl convention]. Phil Richards is looking into using
mpl::vector which may make this trivial, YANL provides potentially unlimited
dimensions) I dont about the others but if you dont require the scaling in
pqs you merely let the extra unit params default. In SI terms this would be
like only using metres,seconds, N etc. The si prefixes (km,us etc)and
incoherent-quantities(kgf etc) add complexity which you may not need.
Alternatively pqs does [in SI context]lets you use
'incoherent-quantities'... quantities in natural units fall into this
category In Context Of SI. Will look further into it and hopefully provide
docs/demo on this aspect at some stage.  I think I am correct in saying that
all the libs are based on one D.A / units logic. S.I. is one 'context' which
is applied above that basic logic.

Note: As far as pqs series is concerned I will obviously have to do a lot of
work on designing tests before putting to use in a 'serious' context.

regards
Andy Little