Re: [Boost-users] [units][accumulators] buggy behavior for min accumulator of quantities

Subject: Re: [Boost-users] [units][accumulators] buggy behavior for min accumulator of quantities
From: alfC (alfredo.correa_at_[hidden])
Date: 2011-03-12 19:45:57

Answering to myself:

On Mar 12, 3:04 pm, alfC <alfredo.cor..._at_[hidden]> wrote:
> Hi,
>  Sometimes it is difficult to make boost::units quantities with other
> libraries. For example to have boost::accumulators mean work with
> units, one has to specialize division by integer for quantities.
>
> In this example the accumulators and units compiles out of the box but
> gives an incorrect answer.

I found the solution, just add

#include<boost/units/limits.hpp>

in this way the min/max function can initialize the default maximum/
minimum value, which is given by the numeric limits of the type.

Anyway, I would suggest to the authors of boost.units to include
limits.hpp by default in the core library in order *to avoid this
surprises*.
Or better yet, make the author of boost.accumulators to support
boost.units.

By the way I made boost accumulators to work with min, max (see above)
and mean by adding the below code. Variance, etc. is more difficult to
implement because boost.accumulators assumes that t*t is always of
type t.

namespace boost {namespace numeric{namespace functional{
        using namespace boost::units;

        template<class Unit, typename Y> struct quantity_tag{};
        template<class Unit, typename Y> struct tag<quantity<Unit,Y> >{
                typedef quantity_tag<Unit,Y> type;
        };

        template<typename Left, typename Right>
        struct average<Left, Right, quantity_tag<typename Left::unit_type,
typename Left::value_type>, void>{
                typedef Left result_type;
                result_type operator()(Left & left, Right & right) const{
                        return left/(typename Left::value_type)right;
                }
           };
}}}

Thanks,
Alfredo