public static IAtom ToSubset(IAtom a, Graph g, int u)
{
// atom is already a subset atom
if (a.Subset)
{
return(a);
}
// element is not organic and thus cannot be part of the subset
if (!a.Element.IsOrganic())
{
return(a);
}
// if any of these values are set the atom cannot be a subset atom
if (a.Charge != 0 || a.AtomClass != 0 || a.Isotope >= 0)
{
return(a);
}
IAtom subset = a.IsAromatic() ? AtomImpl.AromaticSubset.OfElement(a.Element)
: AtomImpl.AliphaticSubset.OfElement(a.Element);
// does the implied availableElectrons from the bond Order sum match that
// which was stored - if aromatic we only check the lowest valence state
int impliedHCount = subset.GetNumberOfHydrogens(g, u);
// mismatch in number of hydrogens we must write this as a bracket atom
return(impliedHCount != a.NumOfHydrogens ? a : subset);
}
