#include <iostream>
    
    using namespace std;
    
    // Definition for Class SL
    class SL {
    private: // Each object contains two values
        int *ptr;  // Pointer to int
        int val;   // Just an int
    public: // Member functions
        SL();
        ~SL();
        SL(const SL &);
        void Readin();
        void Printout();
        void Erase();
    };
    
    // Constructor for Class SL
    SL::SL()
    {ptr = 0;
     cout << "allocated SL " << this << endl;
    }
    
    SL::~SL()
    {cout << "deallocated SL " << this << endl;
     this->Erase();}
    
    // Copy Constructor for Class SL
    SL::SL(const SL & fr)
    {cout << "Copy Constructructor from SL " << &fr << " to SL " << this << endl;
       this->val = fr.val;
       this->ptr = 0;
       if (fr.ptr)
          {ptr = new int;
           *ptr = *(fr.ptr);
          }
       return;
    }
    
    
    void SL::Printout() // Printing out the contents of a SL
    {
       if (ptr == 0)
          {cout << "data " << " 0 value none int " << val << endl; return;}
       cout << "data " << ptr << " value " << *ptr << " int " << val << endl;
       return;
    }
    
    void SL::Readin()  // Reading in the contents of a SL
    { cout << "Input one value" << endl;
      ptr = new int;
      cin >> *ptr >> val;
    }
    
    void SL::Erase() {
       delete(ptr);
       ptr=0;
    }
    
    int main()
    {
      cout << endl;
    
      SL l;    //A30
      l.Readin();
      cout << "SL l" << " Located at " << &l << endl;
      l.Printout();
      cout << endl;
        //  A30   A08   4   3
    
      SL m;    //  A20
      m.Readin();
      cout << "SL m"  << " Located at " << &m<< endl;
      m.Printout();
      cout << endl;
        //  A20   A18   2   1
    
      SL o = m;   //   A10
    //  There is a correct copy constructor so it works
      cout << "SL o"  << " Located at " << &o<< endl;
      o.Printout();
      cout << endl;
        // Copy A20 to A10
        // A10   A28   2   1
    
      l.Erase();
      m.Erase();
    
    // Ok to use the o list after this point
    
      cout << "SL l"  << " Located at " << &l<< endl;
      l.Printout();
        //  A30   A0   ---   3
      cout << "SL m"  << " Located at " << &m<< endl;
      m.Printout();
        //  A20   A0   ---   1
      cout << "SL o"  << " Located at " << &o<< endl;
      o.Printout();
        //  A10  A28   2   1
      cout << endl;
    
      return 0;
    }