Add operators for + and +=

Author: mfasDa

its/Digit.cxx

@@ -28,6 +28,18 @@ fLabels()
 
 Digit::~Digit(){}
 
+Digit &Digit::operator+=(const Digit &other){
+  fCharge += other.fCharge;
+  return *this;
+}
+
+const Digit Digit::operator+(const Digit &other){
+  Digit result(*this);
+  result += other;
+  return result;
+}
+
+
 std::ostream &Digit::Print(std::ostream &output) const{
   output << "ITS Digit of chip index [" << fChipIndex << "] and pixel [" << fPixelIndex << "]with charge " << fCharge << " at time stamp" << fTimeStamp;
   return output;

its/Digit.h

@@ -16,6 +16,9 @@
 namespace AliceO2{
   namespace ITS{
 
+    /// \class Digit
+    /// \brief Digit class for the ITS
+    ///
     class Digit : public FairTimeStamp {
     public:
 
@@ -32,6 +35,19 @@ namespace AliceO2{
       /// Destructor
       virtual ~Digit();
 
+      /// Addition operator
+      /// Adds the charge of 2 digits
+      /// @param lhs First digit for addition (also serves as time stamp)
+      /// @param rhs Second digit for addition
+      /// @return Digit with the summed charge of two digits and the time stamp of the first one
+      const Digit operator+(const Digit &other);
+      
+      /// Operator +=
+      /// Adds charge in other digit to this digit
+      /// @param other Digit added to this digit
+      /// @return Digit after addition
+      Digit &operator+=(const Digit &other);
+      
       /// Get the index of the chip
       /// @return Index of the chip
       ULong_t GetChipIndex() const { return fChipIndex; }