counten.cpp

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// counten.cpp
// inheritance with Counter class
#include <iostream>
using namespace std;
////////////////////////////////////////////////////////////////
class Counter                            //base class
   {
   private:                            //NOTE: not private
      unsigned int count;                //count
   public:
      Counter() : count(0)               //no-arg constructor
         {  }
      Counter(int c) : count(c)          //1-arg constructor
         {  }
      unsigned int get_count() const     //return count
         { return count; }
      Counter operator ++ ()             //incr count (prefix)
         { return Counter(++count); }
   };
////////////////////////////////////////////////////////////////
class CountDn : public Counter           //derived class
   {
   public:
      Counter operator -- ()             //decr count (prefix)
         { return Counter(--count); }
   };
////////////////////////////////////////////////////////////////
int main()
   {
   CountDn c1;                           //c1 of class CountDn

   cout << "\nc1=" << c1.get_count();    //display c1

   ++c1; ++c1; ++c1;                     //increment c1, 3 times
   cout << "\nc1=" << c1.get_count();    //display it

   --c1; --c1;                           //decrement c1, twice
   cout << "\nc1=" << c1.get_count();    //display it
   cout << endl;
   return 0;
   }