1 #include <iostream>
2
3 using namespace std;
4
5 class ComputeBase
6 {
7 public:
8 //virtual 拼写出错
9 //没写成纯虚函数，没有写实现，会出现链接错误
10 virtual double operation(double pre, double next) = 0;
11 };
12
13 class Add: public ComputeBase
14 {
15 public:
16 virtual double operation(double pre, double next);
17 };
18
19 double Add::operation(double pre, double next)
20 {
21 return pre+next;
22 }
23
24 class Sub: public ComputeBase
25 {
26 public:
27 virtual double operation(double pre, double next);
28 };
29
30 double Sub::operation(double pre, double next)
31 {
32 return pre - next;
33 }
34
35 class Mul: public ComputeBase
36 {
37 public:
38 virtual double operation(double pre, double next);
39 };
40
41 double Mul::operation(double pre, double next)
42 {
43 return pre * next;
44 }
45
46 class Div: public ComputeBase
47 {
48 public:
49 virtual double operation(double pre, double next);
50 };
51
52 double Div::operation(double pre, double next)
53 {
54 if(next == 0)
55 {
56 cout << "除数不能为0" << endl;
57 return 0;
58 }
59 return pre / next;
60 }
61 class Simplefactory
62 {
63 private:
64 ComputeBase * pBase;
65 public:
66 Simplefactory(unsigned char cInput);
67 ~Simplefactory();
68 double compute(double pre, double next);
69 };
70
71 Simplefactory::Simplefactory(unsigned char cInput)
72 {
73 switch(cInput)
74 {
75 case '+':
76 pBase = new Add; break;
77 case '-':
78 pBase = new Sub; break;
79 case '*':
80 pBase = new Mul; break;
81 case '/':
82 pBase = new Div; break;
83 default:
84 cout << "undifined compution!" <<endl;
85 }
86 }
87
88 Simplefactory::~Simplefactory()
89 {
90 if(pBase != NULL)
91 delete pBase;
92 }
93 double Simplefactory::compute(double pre, double next)
94 {
95 return pBase->operation(pre, next);
96 }
97
98 int main()
99 {
100 double pre, next;
101 char cCompute;
102 cout << "Please input two operators:" << endl;
103 cin >> pre >> next;
104 cout << "Please input the computor " << endl;
105 cin >> cCompute;
106 Simplefactory fact(cCompute);
107 cout << fact.compute(pre, next) << endl;
108 return 0;
109 }
