SpacePoint.h

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////////////////////////////////////////////////////////////////////////////
//
// Definition of SpacePoint class for LArSoft
//
// SpacePoints are 3D objects that contain pointers to Hits from multiple
// wireplanes that have been identified as matching.
//
// msoderbe@syr.edu
//
////////////////////////////////////////////////////////////////////////////

#ifndef SPACEPOINT_H
#define SPACEPOINT_H

#include <iosfwd>

#include "larcoreobj/SimpleTypesAndConstants/geo_vectors.h"
#include "larcoreobj/SimpleTypesAndConstants/PhysicalConstants.h"
#include <RtypesCore.h>

namespace recob {

  class SpacePoint {

  public:
    using ID_t = int; ///< type of spacepoint ID

    /// Special value for an invalid ID.
    static constexpr ID_t InvalidID = util::kBogusI;


    SpacePoint();  ///Default constructor

  private:
    ID_t                       fID;        ///< SpacePoint ID
    Double32_t                 fXYZ[3];    ///< position of SpacePoint in xyz
    Double32_t                 fErrXYZ[6]; ///< Error matrix (lower triangular).
    Double32_t                 fChisq;     ///< Chisquare.

  public:
    SpacePoint(Double32_t const*xyz,
               Double32_t const*err,
               Double32_t  chisq,
               int     id=InvalidID);

    ID_t                       ID()      const;
    const Double32_t*              XYZ()     const;
    const Double32_t*              ErrXYZ()  const;
    Double32_t                     Chisq()   const;

    /// Returns the position of the point in world coordinates [cm]
    geo::Point_t position() const;

    /// Returns the error matrix element for two position coordinates
    /// (`0` for _x_, `1` for _y_ and `2` for _z_)
    double covariance(unsigned int i, unsigned int j) const;

    /// Returns the internal index of correlation structure for coordinates `i` and `j`.
    static constexpr std::size_t covIndex(unsigned int i, unsigned int j);
    
    friend std::ostream& operator << (std::ostream& o, const SpacePoint & a);
    friend bool          operator <  (const SpacePoint & a, const SpacePoint & b);


  };

  /// Comparison of a space point with an ID, for sorting and lookup.
  inline bool operator< (SpacePoint const& s, SpacePoint::ID_t id) { return s.ID() < id; }
  /// Comparison of a space point with an ID, for sorting and lookup.
  inline bool operator< (SpacePoint::ID_t id, SpacePoint const& s) { return id < s.ID(); }

}


inline recob::SpacePoint::ID_t recob::SpacePoint::ID() const { return fID; }
inline const Double32_t* recob::SpacePoint::XYZ()     const { return fXYZ;    }
inline const Double32_t* recob::SpacePoint::ErrXYZ()  const { return fErrXYZ; }
inline Double32_t        recob::SpacePoint::Chisq()   const { return fChisq;  }

inline geo::Point_t recob::SpacePoint::position() const { return geo::Point_t{ fXYZ[0], fXYZ[1], fXYZ[2] }; }


#endif //SPACEPOINT_H