// READWRIT.CPP -- distinguishing between reads and writes

#include <iostream.h>

template<class T> class proxy {

// proxy is a type created just to cause conversions so
// client code can distinguish between reads and writes.
// Note that all conversion operations are defined in this
// class.

  public:

  // promotion constructor - used when saving a pointer to object
    proxy(T *tptr) { cout << "saving ptr -- "; data = tptr; }

  // assignment - used when writing a T to a proxy
    void operator=(const T &t) {
      cout << "writing value = " << t; *data = t;
    }

  // cast operator - used when reading a T from a proxy
    operator const T() {
      cout << "reading value = " << *data; return *data;
    }

  private:
    T *data;     // a pointer back to original object
};

template<class T> class array {

  public:
    array(int size=10) { _data = new T[_size=size]; }
    int size() { return _size; }

  // note that operator[] returns a proxy
    proxy<T> operator[](int n) { return (_data+n); }

  private:
      T *_data;
    int _size;
};

void msg(char* s) { cout << s; };

void main() {

  cout << "\n\ntesting reads and writes\n";

  msg("\nstatement #1: "); array<int> test1(5);
  msg("\nstatement #2: "); test1[0] = 4;
  msg("\nstatement #3: "); int xi = test1[0];
  cout << endl;

  msg("\nstatement #4: "); array<double> test2(5);
  msg("\nstatement #5: "); test2[0] = 4.55;
  msg("\nstatement #6: "); double xd = test2[0];
  cout << endl;
}