double OECalculateMolecularWeight(const OEMolBase &mol, bool iso = false)
This function calculates the molecular weight of the given molecule. By
default, all atoms are assumed their average atomic weight, as returned
by the OEGetAverageWeight
function. If the `iso' parameter is
true, and atom of the molecule that has a specified (non-zero) isotopic
mass, as returned by OEAtomBase::GetIsotope
, instead uses the
isotopic weight as returned by the OEGetIsotopicWeight
function.