Convenience method for inverting the label of tetrahedral stereochemistry.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Use permutation parity instead of projecting the ligands and then checking for duplicates. Not only is this faster but it extends more naturally to E/Z labelling.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
CIP labels for double-bond - one small adjustment (next commit).

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Double-bond labelling needs ligands in descending order (highest first).

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>
Utility to label all stereo elements.

Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>