text: # <<BEGIN-copyright>>
  # Copyright 2021, Lawrence Livermore National Security, LLC.
  # See the top-level COPYRIGHT file for details.
  # 
  # SPDX-License-Identifier: BSD-3-Clause
  # <<END-copyright>>
  
  # Values from CODATA 2014.
  c = '299792458. * m / s'                  # speed of light (exact)
  mu0 = '4.e-7 * pi * N / A**2'             # permeability of vacuum
  Grav = '6.67408e-11 * m**3 / kg / s**2'   # gravitational constant
  hplanck = '6.626070040e-34 * J * s'         # Planck constant
  e = '1.6021766208e-19 * C'                  # elementary charge
  me = '9.10938356e-31 * kg'                 # electron mass
  mp = '1.672621898e-27 * kg'                # proton mass
  Nav = '6.022140857e23 / mol'                # Avogadro number
  k = '1.38064852e-23 * J / K'               # Boltzmann constant
  amu = '1.660539040e-27 * kg'               # atomic mass unit
  
  # Values from various other places.
  tsp = '4.92892159375 * ml'                # teaspoon
  galUK = '4.54609 * l'                     # British gallon
  oz = '28.349523125 * g'                   # ounce
  cal = '4.184 * J'                         # thermochemical kilocalorie
  cali = '4.1868 * J'                       # international calorie
  Btu = '1055.05585262 * J'                 # British thermal unit
  hp = '745.699872 * W'                     # horsepower
  atm = '101325. * Pa'                      # standard atmosphere pressure
  psi = '6894.75729317 * Pa'                # pounds per square inch
  
  # defC and defF
  