Re: [Boost-users] Boost.Units and Ublas and Math

From: Matthias Schabel (boost_at_[hidden])
Date: 2008-06-25 14:32:16

> Pat Hawley wrote:
>> My next step would be to add units to the numeric values--assuming  
>> this can be
>> done in the context of ublas.
>>
>> Is it possible to use Boost.Units and Boost.Ublas together?
>> For example create a ublas vector of positions?
>>
>
> It is possible to create such a vector, but there isn't a whole lot
> you can do with it.  You certainly won't be able to do anything
> that requires quantities to be multiplied and divided inside uBlas.

The problem being that ublas currently does not correctly resolve the  
value type for arithmetic operations. For "normal" numeric types, even  
if not strictly correct, this is usually not a problem : the type of  
vector<double>*vector<double> is vector<double>. Since all the unit  
magic in Boost.Units is encoded in the types, this isn't true with  
quantities : the type of vector<quantity<length>  
 >*vector<quantity<length> > is vector<quantity<area> >... In  
principle, this could be fixed, but would require a significant amount  
of effort on the part of the ublas maintainers.

Matthias