插入运算符“＞＞“和提取运算符“＜＜“的重载

1. #include<iostream>
2. using namespace std;
3. class A
4. {
5. public:
6. A(int b=0):a(b)
7.     {
8.         ;
9.     }
10. int a;
11.     ostream& operator<<(ostream& out)
12.     {
13.         out<<a;
14. return out;
15.     }
16. friend ostream& operator<<(ostream& out,A& ptr);
17. };
18. ostream& operator<<(ostream& out,A& ptr)
19. {
20.     out<<ptr.a;
21. return out;
22. }
23. void test1()
24. {
25. A a(520);
26.     a.operator<<(cout)<<endl;
27.     a<<cout<<"大河之水天上来"<<endl;
28. }
29. void test2()
30. {
31. A a(1314);
32. operator<<(cout,a)<<endl;
33.     cout<<a<<"奔流到海不复回"<<endl;
34. }
35. int main()
36. {
37. //如果使用成员函数来重载,使用起来就非常的迷惑，必须把自己定义的类对象写前面， a<<cout,这种形式就很奇怪
38. test1();
39. //使用友元函数来重载，代码的可读性增强，cout<<a
40. test2();
41. return 0;
42. }
43. 结果：
44. 520
45. 520大河之水天上来
46. 1314
47. 1314奔流到海不复回

1. #include<iostream>
2. using namespace std;
3. class Timer
4. {
5. public:
6. Timer()
7.     {
8.       hours=0;
9.       minutes=0;
10.     }
11. Timer(int h,int m):hours(h),minutes(m)
12.     {
13.         ;
14.     }
15. friend Timer operator+(Timer& pf,Timer& pc);
16. friend Timer operator-(Timer& pf,Timer& pc);
17. friend ostream& operator<<(ostream& out,Timer& ptr);
18. friend istream& operator>>(istream& in,Timer& ptr);
19. private:
20. int hours;
21. int minutes;
22. };
23. Timer operator+(Timer& pf,Timer& pc)
24. {
25.     Timer ptr;
26.     ptr.minutes=pf.minutes+pc.minutes;
27.     ptr.hours=pf.hours+pc.hours+ptr.minutes/60;
28.     ptr.minutes%=60;
29. return ptr;
30. }
31. Timer operator-(Timer& pf,Timer& pc)
32. {
33.     Timer ptr;
34. int x;
35.     x=pf.hours*60+pf.minutes-pc.hours*60-pc.minutes;
36.     ptr.hours=x/60;
37.     ptr.minutes=x%60;
38. return ptr;
39. }
40. ostream& operator<<(ostream& out,Timer& ptr)
41. {
42.     out<<ptr.hours<<" hours"<<","<<ptr.minutes<<" minutes";
43. return out;
44. }
45. istream& operator>>(istream& in,Timer& ptr)
46. {
47.     cout<<"Input hours and minutes:";
48.     in>>ptr.hours>>ptr.minutes;
49. return in;
50. }
51. int main()
52. {
53.     Timer t1,t2,t3,t4;
54.     cin>>t1>>t2;
55.     cout<<"t1="<<t1<<endl;
56.     cout<<"t2="<<t2<<endl;
57.     t3=t1+t2;
58.     cout<<"t3=t1+t2="<<t3<<endl;
59.     t4=t1-t2;
60.     cout<<"t4=t1-t2="<<t4<<endl;
61. return 0;
62. 
63. }
64. 运行结果：
65. Input hours and minutes:23 13
66. Input hours and minutes:21 39
67. t1=23 hours,13 minutes
68. t2=21 hours,39 minutes
69. t3=t1+t2=44 hours,52 minutes
70. t4=t1-t2=1 hours,34 minutes
71. 
72.