PFMatch::EtaPhiSqDistanceCalculator Node1 PFMatch::EtaPhiSqDistance Calculator + EtaPhiSqDistanceCalculator() + ~EtaPhiSqDistanceCalculator() + distanceBetween() Node2 PFMatch::DistanceCalculator < EtaPhi, EtaPhi > + ~DistanceCalculator() + distanceBetween() # DistanceCalculator() Node2->Node1