text: #ifndef PROJECT1_STATISTICIAN_H
  #define PROJECT1_STATISTICIAN_H
  
  namespace project1_statistician_h{
      class Statistician {
          public:
              Statistician();
              Statistician(double last_num, double min_num, double max_num, double total_sum, int length);
      
              void erase();
              void next_number(double number);
              double get_minimum() const;
              double get_maximum() const;
              double get_sum() const;
              double get_length() const;
              double get_last() const;
  
              // Statistician operator+(const Statistician& s2);
  
              // friend function
              // friend Statistician operator+ (const Statistician& s1, const Statistician& s2);
  
          private:
              double sequence_min;
              double sequence_max;
              double sequence_sum;
              double sequence_last;
              int sequence_length;
  
      };
      
      Statistician operator + (const Statistician& s1, const Statistician& s2);
      
  }
  
  
  #endif