RhoDoubleErr.h

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//*                   This file is part of PandaRoot.                        *
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//*            PandaRoot is distributed under the terms of the               *
//*              GNU General Public License (GPL) version 3,                 *
//*                 copied verbatim in the file "LICENSE".                   *
//*                                                                          *
//*  Copyright (C) 2006 - 2024 FAIR GmbH and copyright holders of PandaRoot  *
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#ifndef RHODOUBLEERR_H
#define RHODOUBLEERR_H
//                                                                      //
// RhoDoubleErr                                                         //
//                                                                      //
// Double w/ error                                                      //
//                                                                      //
// Author: Marcel Kunze, RUB, Nov. 99                                   //
// Copyright (C) 1999-2001, Ruhr-University Bochum.                     //
// Ralf Kliemt, HIM/GSI Feb.2013 (Cleanup & Restructuring)              //
//                                                                      //

// Description:
// Class TDoubleErr holds a Double_t and its error squared,
// the equivalent of a TVectorErr with one dimension.
//
// determineChisq(Double_t ref) returns (ref-value())^2 / covariance().
// If the covariance() <= 0 then returns TError::chisqUndef.
//
// The mathematical operators can be used to correctly take into account
// error propagation through simple mathematical operations. Beware of
// operations whose covariance may not be the same as the one which
// results from a sequence of simple operations. For example, a*a will give
// the wrong covariance, since the algorithm assumes that the two arguments
// of the operator* are independent.

#include "TBuffer.h"
#include "TObject.h"
#include "RhoError.h" // for chisqUndef only

class RhoDoubleErr : public TObject {
 public:
  // Constructors: The fCovariance and the fValue are 0.0 unless specified:
  RhoDoubleErr() : fValue(0.0), fCovariance(0.0){};
  RhoDoubleErr(Double_t val) : fValue(val), fCovariance(0.0){};
  RhoDoubleErr(Double_t val, Double_t cov) : fValue(val), fCovariance(cov){};

  // Copy Constructor
  RhoDoubleErr(const RhoDoubleErr &);

  // Destructor
  virtual ~RhoDoubleErr() {}

  // Assignment operator:
  RhoDoubleErr &operator=(const RhoDoubleErr &);

  // Accessors (const)
  Double_t Value() const { return fValue; }
  Double_t Covariance() const { return fCovariance; }
  Double_t DetermineChisq(Double_t ref) const;

  RhoDoubleErr operator-(); // value() -> -value(), covariance() unaffected
  RhoDoubleErr operator-(const RhoDoubleErr &);
  RhoDoubleErr operator+(const RhoDoubleErr &);

  // NOTE: (a * b).covariance() is
  // b^2 * a.covariance() + a^2 * b.covariance()
  RhoDoubleErr operator*(const RhoDoubleErr &);

  // NOTE: (a / b).covariance() is
  // a.covariance() / b^2 + b.covariance() * a^2 / b^4
  RhoDoubleErr operator/(const RhoDoubleErr &);

  // modifiers:
  void SetValue(Double_t val) { fValue = val; }
  void SetCovariance(Double_t cov) { fCovariance = cov; }

  RhoDoubleErr &operator+=(const RhoDoubleErr &);
  RhoDoubleErr &operator-=(const RhoDoubleErr &);
  RhoDoubleErr &operator*=(const RhoDoubleErr &);
  RhoDoubleErr &operator/=(const RhoDoubleErr &);

  // needed for RWTValOrderedVector
  Bool_t operator==(const RhoDoubleErr &other) const { return (fValue == other.fValue && fCovariance == other.fCovariance); }
  Bool_t operator<(const RhoDoubleErr &other) const { return (fValue < other.fValue); }

 private:
  // Data members
  Double_t fValue;
  Double_t fCovariance;

 public:
  ClassDef(RhoDoubleErr, 1) // holds a Double_t and its error squared
};

std::ostream &operator<<(std::ostream &stream, const RhoDoubleErr &bde);

#endif