DistanceFunctor.h

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef DISTANCE_FUNCTOR_H
#define DISTANCE_FUNCTOR_H
 
#include <math.h>
 
template <typename T, typename U>
class DistanceFunctor {
 
  public:
    float operator()(const T *t, const U *u) const {
      return calculateDistance(t, u);
    }
 
    float distance(const T *t, const U *u) const {
      return (*this)(t, u);
    }
 
    virtual ~DistanceFunctor() {;}
 
  private:
    virtual float calculateDistance(const T *t, const U *u) const = 0;
 
}; // end class DistanceFunctor
 
template <typename T, typename U>
class DeltaRDistanceFunctor : virtual public DistanceFunctor<T, U> {
 
  public:
 
    virtual ~DeltaRDistanceFunctor() {;}
 
    static float deltaR(const T *t, const U *u) {
 
      if(!t || !u)
        return -1.;
 
      float phiDiff = t->phi() - u->phi();
      while(phiDiff < -M_PI) phiDiff += 2. * M_PI;
      while(phiDiff >= M_PI) phiDiff -= 2. * M_PI;
      float etaDiff = t->eta() - u->eta();
      return sqrt(phiDiff * phiDiff + etaDiff * etaDiff);
 
    }
 
  private:
 
    virtual float calculateDistance(const T *t, const U *u) const {
      return DeltaRDistanceFunctor<T,U>::deltaR(t, u);
    }
 
}; // end class DeltaRDistanceFunctor
 
#endif