unsigned int OEGetHBondDonorCount(const OEChem::OEMolBase &mol)
Returns the number of hydrogen-bond donors in a molecule based on the definition in the work of Mills and Dean ([MillsDean-1996]) and also in the book by Jeffrey ([Jeffrey-1997]). It is defined to be the number of hydrogen atoms on nitrogen, oxygen, or sulfur atoms.
OEGetHBondDonorCount function returns
2 for the molecule below.