Dear users,
I just started to use boost::units for some simulations. However, I have
some problems with unit conversions and I hope someone can help me.
Let's say I have a quantity given in terms of energy in "electron volts"
(eV) with the unit "energy". I defined the unit the following:
BOOST_UNITS_DEFINE_BASE_UNIT_WITH_CONVERSIONS(si, electron_volts,
"electron volts", "eV", PHYSICAL_CONSTANT_DVALUE(e), si::energy, 5000);
namespace si {
typedef make_system::type
electron_volt_system;
typedef unit
electron_volt_type;
BOOST_UNITS_STATIC_CONSTANT(eV,electron_volt_type);
}
where PHYSICAL_CONSTANT_DVALUE(e) gives me the double representation of
si::constants::codata::e.value().
This works fine, for conversions like eV=>Joule etc.
(By the way, is there a more straight forward way, to define
non-rational scaled units, than defining a new unit sytem?)
Now I want to convert eV to nanometers (wavelength)
This is defined as:
wavelength = c/frequency = h*c/energy
(c=speed of light, h = Planck's constant)
I would again define a system with the base unit of wavelength and the
unit wavelength_type initialized e.g. with wavelength_nanometer.
First Problem:
What would be the derived dimension/unit: energy, length or a new
dimension like wavelength_dimenson?
If I would define it as something else than energy, I will have problems
when using quantitysi::electron_volt_type(x*si::wavelength_nanometer)
or quantitysi::nanometer_type(x*si::eV)
Second problem:
The relationship is reciprocal: wavelength ~ 1/energy. How do I define a
proper conversion?
Thanks for your help!
Cheers,
Matthias
