#    Units definition file for pint library

#    This file defines additional units and contexts to enable the pint
#    library to process solution chemistry units such as mol/L and mol/kg.

@context(mw=0,volume=0,solvent_mass=0) chemistry = chem
    # mw is the molecular weight of the species
    # volume is the volume of the solution
    # solvent_mass is the mass of solvent in the solution

    # moles -> mass require the molecular weight
    [substance] -> [mass]: value * mw
    [mass] -> [substance]: value / mw

    # moles/volume -> mass/volume and moles/mass -> mass / mass
    # require the  molecular weight
    [substance] / [volume] -> [mass] / [volume]: value * mw
    [mass] / [volume] -> [substance] / [volume]: value / mw
    [substance] / [mass] -> [mass] / [mass]: value * mw
    [mass] / [mass] -> [substance] / [mass]: value / mw

    # moles/volume -> moles requires the solution volume
    [substance] / [volume] -> [substance]: value * volume
    [substance] -> [substance] / [volume]: value / volume

    # moles/mass -> moles requires the solvent (usually water) mass
    [substance] / [mass] -> [substance]: value * solvent_mass
    [substance] -> [substance] / [mass]: value / solvent_mass

    # moles/mass -> moles/volume require the solvent mass and the volume
    [substance] / [mass] -> [substance]/[volume]: value * solvent_mass / volume
    [substance] / [volume] -> [substance] / [mass]: value / solvent_mass * volume

@end

@context electricity = elec
    [length] ** 2 * [mass] / [current] ** 2 / [time] ** 3 <-> [length] ** -2 * [mass] **-1 / [current] ** -2 / [time] ** -3: 1 / value
@end


#From the pint documentation:

#@context(n=1) spectroscopy = sp
#    # n index of refraction of the medium.
#    [length] <-> [frequency]: speed_of_light / n / value
#    [frequency] -> [energy]: planck_constant * value
#    [energy] -> [frequency]: value / planck_constant
#@end

# The @context directive indicates the beginning of the transformations which are finished by the @end statement. You can optionally specify parameters for the context in parenthesis. All parameters are named and default values are mandatory. Multiple parameters are separated by commas (like in a python function definition). Finally, you provide the name of the context (e.g. spectroscopy) and, optionally, a short version of the name (e.g. sp) separated by an equal sign.
# Conversions rules are specified by providing source and destination dimensions separated using a colon (:) from the equation. A special variable named value will be replaced by the source quantity. Other names will be looked first in the context arguments and then in registry.
# A single forward arrow (->) indicates that the equations is used to transform from the first dimension to the second one. A double arrow (<->) is used to indicate that the transformation operates both ways.
