Re: [boost] [units] Crazy idea/question

From: Steven Watanabe (steven_at_[hidden])
Date: 2007-02-16 13:51:07

AMDG

Matthias Schabel <boost <at> schabel-family.org> writes:

> 
> >> 1) The target unit may only have one instance of each tag (no
> >> repeated tags with different
> >> systems). Otherwise, the conversion becomes ambiguous.
> >
> > If the source has only one instance of each tag
> > than it should be easy too.
> 
> But in general we should assume that constructs like this are legit:
> 
> quantity<SI::volume>	V(1.0*SI::meters*imperial::feet*CGS::centimeters);
> 
> where the system of the result type defines the conversions
> 
> imperial::feet->SI::meters
> CGS::centimeters->SI::meters
> 
> to get the conversion factor...this is unambiguous in all cases, AFAICS.

I didn't mean that it shouldn't be valid.  I meant
that both should be allowed.  Otherwise, conversions
are not necessarily reversible.

In Christ,
Steven Watanabe