Re: [Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric)

AMDG On 11/20/2018 06:46 PM, Matt Vinson via Boost-users wrote:

<snip> <some reformatting to reduce line wrapping> *.h-----------------------------------------------------

namespace dimensional_analysis {

    typedef length_base_dimension::dimension_type length_dimension;     typedef mass_base_dimension::dimension_type mass_dimension;

typedef make_system::type ip_system;

This should be pound_force_base_unit.

  namespace lineal_force {     typedef mpl::divides::type lineal_force_dimension;          

    namespace imperial {

      ////////////////       ////lb/in, right?

////boost::units::force_dimension =pound ////boost::units::length_dimension = in       ////////////////       typedef unit lineal_force_unit;

This unit is nonsensical because the ip_system as written is unable to represent the lineal_force_dimension. That this doesn't give a hard compiler error is a bug in the library. Once you fix ip_system, the conversions should be right.

    }     namespace si {     ////////////////     ////N/m, right?

Yep.

////boost::units::force_dimension = newton ////boost::units::length_dimension = meter       ////////////////       typedef unit lineal_force_unit;     }   }//lineal_force }//dimensional_analysis

*.cpp-----------------------------------------------------

//Imperiallb/in to SI N/m

The following conversion definitions are unnecessary and have no effect:

BOOST_UNITS_DEFINE_CONVERSION_FACTOR( dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit, double, 175.1268369864); // exact conversion

BOOST_UNITS_DEFAULT_CONVERSION( dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit);

//SI N/mto Imperial lb/in

BOOST_UNITS_DEFINE_CONVERSION_FACTOR( dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit, double, 0.1837185501); // exact conversion

BOOST_UNITS_DEFAULT_CONVERSION( dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit);

<snip>

In Christ, Steven Watanabe