RFC: SI Units facility for Phobos

[Jonathan M Davis]

On Wednesday, January 05, 2011 15:40:37 BCS wrote:
> Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> wrote:
> > (c) Numeric issues as I described (and no amount of rhetoric will set
> > that straight; FWIW given the obvious question of scaling you need to
> > prove it works, not me to prove it doesn't)
> > (d) Unrealized potential (if we approve this, backward compatibility
> > will prevent more comprehensive libraries having the same aim but a
> > different design). This argument is to be taken with a grain of salt as
> > in general it can be easily abused. What I'm saying is that once this
> > library is in we may as well forget about scaled units a la boost units
> > (which are the kind I'd want to use).
> 
> We have both said our piece on these, what do others think? I'd be
> particularly interested in what Don has to say on the numeric issues. Does
> an extra layer or two of FP rounding really mater.

Personally, I tend to cringe when I see much in the way of floating points in 
anything that needs precision, but it's not like you can avoid it in this case. 
Regardless, I agree with pretty much everything that Andrei has said. I 
particularly don't like that the values are all in meters internal - 
_especially_ when dealing with floating point values. I'd be very worried about 
precision issues. The Boost solution seems like a solid one me. However, I'm not 
likely the sort of person who's going to be using a unit library very often. I 
just don't deal with code that cares about that sort of thing very often.

- Jonathan M Davis