// Test program to determine the mass of a chemical compound.

use elements.frink

// Returns the mass of a molecule of a chemical compound like "H2SO4" or "NaCl"
// To get the molar mass, multiply the results by "avogadro".
mass[compound] :=
{
   mass = 0 amu
   // The regular expression below breaks into pairs of element names
   // and their count.
   for [elem,count] = compound =~ %r/([A-Z][a-z]{0,2})(\d*)/g
   {
      if (! count)
         count = 1
      else
         count = eval[count]
      e = Element.getByName[elem]

      if (e == undef)
         return "Error:  Unknown element $elem.  Note that case is important!"
      else
         mass = mass + e.atomicMass * count
   }
   return mass
}