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- // ex07014.cpp
- // Friend classes, forward reference
- #include <iostream.h>
-
- // -------- Julian date class
- class Julian {
- int da, yr;
- public:
- Julian() {}
- Julian(int d, int y) { da = d; yr = y;}
- void display() {cout << '\n' << yr << '-' << da;}
- friend class Date; // <--- forward reference to class
- };
-
- // ------- date class
- class Date {
- int mo, da, yr;
- public:
- Date(int m, int d, int y) { mo = m; da = d; yr = y; }
- operator Julian();
- };
-
- static int dys[] = {31,28,31,30,31,30,31,31,30,31,30,31};
-
- // ---- member conversion function (Julian <- Date)
- Date::operator Julian()
- {
- Julian jd(0, yr);
- for (int i = 0; i < mo-1; i++)
- jd.da += dys[i];
- jd.da += da;
- return jd;
- }
-
- main()
- {
- Date dt(11,17,89);
- Julian jd;
- jd = dt;
- jd.display();
- }