Re: [Boost-users] [units] conversion_factor in the two directions

26 Feb 2010


      ...
This should not compile.  I'll look into it.  You probably need
to fragment it into SI base units.
yes I was thinking something like that, like creating an
si::energy_base_unit but then it will be full of base units if I do it
this for every dimension. Besides it worked in one direction.
...
If you could provide either
the error message, or even better, the definition of the atomic
system, I could help more.
this is gcc 4.4.1, boost-1.40
error messages, atomic.hpp and main.cpp are attached below.

Thank you,
Alfredo


---begin error message -----------------------------------
In file included from /usr/include/boost/units/conversion.hpp:14,
                 from /usr/include/boost/units/quantity.hpp:29,
                 from eos.cpp:7:
/usr/include/boost/units/detail/conversion_impl.hpp: In instantiation
of
‘boost::units::detail::conversion_impl<1>::apply<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > >’:
/usr/include/boost/units/detail/conversion_impl.hpp:445:
instantiated from
‘boost::units::detail::conversion_factor_helper<boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>, boost::units::dimensionless_type>
...
, void>,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 2l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::atomic::hartree_energy_base_unit,
boost::units::static_rational<-0x00000000000000001l, 2l> >,
boost::units::dimensionless_type> > >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>, boost::units::dimensionless_type>
, void> >’
/usr/include/boost/units/detail/conversion_impl.hpp:274:
instantiated from
‘boost::units::detail::call_base_unit_converter_impl<false>::apply<boost::units::si::second_base_unit,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 2l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::atomic::hartree_energy_base_unit,
boost::units::static_rational<-0x00000000000000001l, 2l> >,
boost::units::dimensionless_type> > >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>, boost::units::dimensionless_type>
, void> >’
/usr/include/boost/units/detail/conversion_impl.hpp:289:
instantiated from
‘boost::units::detail::call_base_unit_converter<boost::units::si::second_base_unit,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 2l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::atomic::hartree_energy_base_unit,
boost::units::static_rational<-0x00000000000000001l, 2l> >,
boost::units::dimensionless_type> > >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>, boost::units::dimensionless_type>
, void> >’
/usr/include/boost/units/detail/conversion_impl.hpp:316:
instantiated from
‘boost::units::detail::conversion_impl<1>::apply<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type>,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > >’
/usr/include/boost/units/detail/conversion_impl.hpp:316:
instantiated from
‘boost::units::detail::conversion_impl<2>::apply<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> >,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > >’
/usr/include/boost/units/detail/conversion_impl.hpp:316:
instantiated from
‘boost::units::detail::conversion_impl<3>::apply<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > >’
/usr/include/boost/units/detail/conversion_impl.hpp:445:
instantiated from
‘boost::units::detail::conversion_factor_helper<boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::dimensionless_type> >, void>,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::atomic::hartree_energy_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::dimensionless_type> >, void> >’
/usr/include/boost/units/detail/conversion_impl.hpp:40:   instantiated
from
‘boost::units::detail::conversion_factor_helper<boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::si::second_base_unit,
boost::units::list<boost::units::si::ampere_base_unit,
boost::units::list<boost::units::si::kelvin_base_unit,
boost::units::list<boost::units::si::mole_base_unit,
boost::units::list<boost::units::si::candela_base_unit,
boost::units::list<boost::units::angle::radian_base_unit,
boost::units::list<boost::units::angle::steradian_base_unit,
boost::units::dimensionless_type> > > > > > > > > >, void>,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::atomic::electron_mass_base_unit,
boost::units::list<boost::units::atomic::bohr_radius_base_unit,
boost::units::list<boost::units::atomic::elementary_charge_base_unit,
boost::units::list<boost::units::atomic::reduced_planck_constant_base_unit,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > > >, void> >’
/usr/include/boost/units/detail/conversion_impl.hpp:345:
instantiated from ‘static boost::units::quantity<Unit2, T2>
boost::units::conversion_helper<boost::units::quantity<Unit1, T1>,
boost::units::quantity<Unit2, T2> >::convert(const
boost::units::quantity<Unit1, T1>&) [with Unit1 =
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::si::second_base_unit,
boost::units::list<boost::units::si::ampere_base_unit,
boost::units::list<boost::units::si::kelvin_base_unit,
boost::units::list<boost::units::si::mole_base_unit,
boost::units::list<boost::units::si::candela_base_unit,
boost::units::list<boost::units::angle::radian_base_unit,
boost::units::list<boost::units::angle::steradian_base_unit,
boost::units::dimensionless_type> > > > > > > > > >, void>, T1 =
double, Unit2 =
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::atomic::electron_mass_base_unit,
boost::units::list<boost::units::atomic::bohr_radius_base_unit,
boost::units::list<boost::units::atomic::elementary_charge_base_unit,
boost::units::list<boost::units::atomic::reduced_planck_constant_base_unit,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > > >, void>, T2 = double]’
/usr/include/boost/units/quantity.hpp:193:   instantiated from
‘boost::units::quantity<Unit, Y>::quantity(const
boost::units::quantity<Unit2, YY>&, typename
boost::disable_if<boost::mpl::and_<typename
boost::units::is_implicitly_convertible<Unit2, Unit>::type,
boost::units::detail::is_non_narrowing_conversion<YY, Y>,
mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >, typename
boost::units::detail::disable_if_is_same<Unit, Unit2>::type>::type*)
[with Unit2 =
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::list<boost::units::si::second_base_unit,
boost::units::list<boost::units::si::ampere_base_unit,
boost::units::list<boost::units::si::kelvin_base_unit,
boost::units::list<boost::units::si::mole_base_unit,
boost::units::list<boost::units::si::candela_base_unit,
boost::units::list<boost::units::angle::radian_base_unit,
boost::units::list<boost::units::angle::steradian_base_unit,
boost::units::dimensionless_type> > > > > > > > > >, void>, YY =
double, Unit =
boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,
boost::units::static_rational<2l, 1l> >,
boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<-0x00000000000000002l, 1l> >,
boost::units::dimensionless_type> > >,
boost::units::homogeneous_system<boost::units::list<boost::units::atomic::electron_mass_base_unit,
boost::units::list<boost::units::atomic::bohr_radius_base_unit,
boost::units::list<boost::units::atomic::elementary_charge_base_unit,
boost::units::list<boost::units::atomic::reduced_planck_constant_base_unit,
boost::units::list<boost::units::atomic::hartree_energy_base_unit,
boost::units::dimensionless_type> > > > > >, void>, Y = double]’
eos.cpp:89:   instantiated from here
/usr/include/boost/units/detail/conversion_impl.hpp:316: error: no
type named ‘type’ in ‘struct
boost::units::detail::call_base_unit_converter<boost::units::si::second_base_unit,
boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>,
boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::meter_base_unit,
boost::units::static_rational<1l, 1l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10l, boost::units::static_rational<3l, 1l> > >,
boost::units::static_rational<1l, 2l> >,
boost::units::list<boost::units::heterogeneous_system_dim<boost::units::atomic::hartree_energy_base_unit,
boost::units::static_rational<-0x00000000000000001l, 2l> >,
boost::units::dimensionless_type> > >,
boost::units::list<boost::units::dim<boost::units::time_base_dimension,
boost::units::static_rational<1l, 1l> >,
boost::units::dimensionless_type>, boost::units::dimensionless_type>
, void> >’
compilation terminated due to -Wfatal-errors.
---end error message --------------------------------
---begin
atomic.hpp---------------------------------------------------------------------------------------------------------------------------------
#include <boost/units/base_unit.hpp>

//equivalent to includes in units/systems/si/base.hpp
#include <boost/units/static_constant.hpp>
#include <boost/units/unit.hpp>
#include <boost/units/make_system.hpp>

//#include <boost/units/io.hpp> //do not remove: '...has initializer
but incomplete type...' error

//equivalent to includes in //equivalent to ./base_units/si/*.hpp
#include <boost/units/config.hpp>
#include <boost/units/base_unit.hpp>
#include <boost/units/scaled_base_unit.hpp>
#include <boost/units/physical_dimensions/mass.hpp>
#include <boost/units/physical_dimensions/length.hpp>
#include <boost/units/physical_dimensions/mass.hpp>
#include <boost/units/physical_dimensions/electric_charge.hpp>
#include <boost/units/physical_dimensions/angular_momentum.hpp>
#include <boost/units/physical_dimensions/energy.hpp>

//equivalent to ./base_units/si/*.hpp
namespace boost{
namespace units{
namespace atomic{   //define namespace au=boost::units::atomic if
necessary
	using std::string;
	// taken from http://en.wikipedia.org/wiki/Atomic_units#Fundamental_units
	struct electron_mass_base_unit : base_unit<electron_mass_base_unit,
mass_dimension, 1>{
		static string name()	{return ("electron_mass");}
		static string symbol()	{return ("me");}
	};
	//equivalent to ./base_units/si/meter.hpp>
	struct bohr_radius_base_unit : base_unit<bohr_radius_base_unit,
length_dimension, 2>{
		static string name()	{return ("bohr_radius");}
 		static string symbol()	{return ("a0");}
 	};
 	struct elementary_charge_base_unit :
base_unit<elementary_charge_base_unit, electric_charge_dimension, 3>{
 		static string name()	{return ("elementary_charge");}
 		static string symbol()	{return ("e");}
 	};
 	struct reduced_planck_constant_base_unit :
base_unit<reduced_planck_constant_base_unit,
angular_momentum_dimension, 4>{
 		static string name()	{return ("reduced_planck_constant");}
 		static string symbol()	{return ("hbar");}
 	};
 	struct hartree_energy_base_unit :
base_unit<hartree_energy_base_unit, energy_dimension, 5>{
 		static string name()	{return ("hartree_energy");}
 		static string symbol()	{return ("Eh");}
 	};
}}}//nss


//similar to ./systems/si/base.hpp
namespace boost{
namespace units{
namespace atomic{
 	typedef make_system<
 		electron_mass_base_unit,
 		bohr_radius_base_unit,
 		elementary_charge_base_unit,
 		reduced_planck_constant_base_unit,
 		hartree_energy_base_unit
 	>::type system;
}}}

//equivalent to units/systems/si/.*.hpp
namespace boost{
namespace units{
namespace atomic{
 	typedef unit<dimensionless_type,	system> dimensionless;
 	typedef unit<mass_dimension,		system> mass;
 	typedef unit<length_dimension,		system> length;
 	typedef unit<electric_charge_dimension,	system> electric_charge;
 	typedef unit<angular_momentum_dimension,system> angular_momentum;
 	typedef unit<energy_dimension, 		system> energy;

 	static const mass		electron_mass;
 	static const length 		bohr_radius, 		bohr;
 	static const electric_charge	elementary_charge;
 	static const angular_momentum 	reduced_planck_constant;
 	static const energy 		hartree_energy, 	hartree;
}}}

#include<boost/units/physical_dimensions.hpp>

//derived, equiv for example to units/systems/si/area.hpp
namespace boost{
namespace units{
namespace atomic{
	typedef unit<area_dimension, 		system> area;
	typedef unit<volume_dimension,		system> volume;
	typedef unit<pressure_dimension, 	system> pressure;
}}}
---end atomic.hpp

---begin
main.cpp-------------------------------------------------------------------------------------------------------------------------------------
#include<boost/units/quantity.hpp>
#include<boost/units/io.hpp>
#include<boost/units/systems/si.hpp>
#include<boost/units/systems/si/io.hpp> //helps transforms the output
from kg/m/s^2 to J

#include<boost/units/systems/si/prefixes.hpp>
#include<boost/units/systems/cgs.hpp>
#include<boost/units/scale.hpp>
#include<boost/units/pow.hpp>
#include"boost/units/atomic.hpp"

//#include <boost/units/systems/si/io.hpp>

#include<iostream>

#include"boost/units/base_units/metric/angstrom.hpp"
namespace boost{
namespace units{
namespace metric{
    typedef metric::angstrom_base_unit::unit_type angstrom_unit;
    BOOST_UNITS_STATIC_CONSTANT(angstrom, angstrom_unit);
}}}

/*
namespace boost { namespace units
{
    typedef metric::angstrom_base_unit::unit_type angstrom_unit;
    BOOST_UNITS_STATIC_CONSTANT(angstrom, angstrom_unit);

    typedef scaled_base_unit<
            si::meter_base_unit,
            scale<10, static_rational<-9> >
	> nanometer_base_unit;
    typedef nanometer_base_unit::unit_type nanometer_unit;
    BOOST_UNITS_STATIC_CONSTANT(nanometer, nanometer_unit);

//    typedef make_scaled_unit<si::length, scale<10,
static_rational<-9> > >::type nanometer;
} } // namespace boost::units
*/
using std::clog;
using std::endl;

using namespace boost::units;
class vinet{
	public:
	class parameters{
		public:
		quantity<atomic::volume> v0; //volume
		quantity<atomic::energy> phi0;
	};
};

BOOST_UNITS_DEFINE_CONVERSION_FACTOR(
       atomic::bohr_radius_base_unit,
       metric::angstrom_base_unit,
       double, 0.529177209
);

#include<boost/units/systems/si/energy.hpp>

BOOST_UNITS_DEFINE_CONVERSION_FACTOR(
	atomic::hartree_energy_base_unit,
	si::energy,
	double, 4.359744e-18
);

//compiles but doesn't help for en3
BOOST_UNITS_DEFINE_CONVERSION_FACTOR(
	si::energy,
	atomic::hartree_energy_base_unit,
	double, 1./4.359744e-18
);

int main(){
	quantity<si::length> l1(1.*si::meter); //works
	quantity<si::length> l2(1.*atomic::bohr); //works
	quantity<atomic::length> l3(1.*atomic::bohr); //works
	quantity<atomic::length> l4(1.*si::meter); //works

	quantity<si::energy> en1(1.*si::joules); //works
	quantity<si::energy> en2(1.*atomic::hartree); //works
	quantity<atomic::energy> en3(1.*atomic::hartree); //work
	quantity<atomic::energy> en4(1.*si::joules); //does not work,
compilation error
	return 0;
}
---end main.cpp

Re: [Boost-users] [units] conversion_factor in the two directions

alfC