union in cplusplus

C++语言: Codee#25730

01 #include <>iostream>
02 using namespace std;
03
04 union U
05 {
06 private:
07     int i;
08     float f;
09 public:
10     U(int a);
11     U(float b);
12     ~U();
13     int read_int();
14     float read_float();
15 };
16
17 U::U(int a)
18 {
19     i = a;
20 }
21
22 U::U(float b)
23 {
24     f = b;
25 }
26
27 U::~U()
28 {
29     cout << "U::~U()\n";
30 }
31
32 int U::read_int()
33 {
34     return i;
35 }
36
37 float U::read_float()
38 {
39     return f;
40 }
41
42 int main()
43 {
44     U x(12), y(1.9f);
45     cout << x.read_int() << endl;
46     cout << x.read_float() << endl;            // just union in c with member functions
47
48     cout << end << y.read_float() << endl;
49
50     return 0;
51 }

C++语言: Codee#25731

01 #include <iostream>
02 using namespace std;
03
04 class SuperVar
05 {
06     enum
07     {
08         character,
09         integer,
10         floating_point
11     } vartype;
12     union
13     {
14         char c;
15         int i;
16         float f;
17     };
18 public:
19     SuperVar(char ch);
20     SuperVar(int ii);
21     SuperVar(float ff);
22     void print();
23 };
24
25 SuperVar::SuperVar(char ch)
26 {
27     vartype = character;
28     c = ch;
29 }
30
31 SuperVar::SuperVar(int ii)
32 {
33     vartype = integer;
34     i = ii;
35 }
36
37 SuperVar::SuperVar(float ff)
38 {
39     vartype = floating_point;
40     f = ff;
41 }
42
43 void SuperVar::print()
44 {
45     switch(vartype)
46     {
47     case character:
48         cout << "character: " << c << endl;
49         break;
50     case integer:
51         cout << "integer: " << i << endl;
52         break;
53     case floating_point:
54         cout << "float: " << f << endl;
55         break;
56     }
57 }
58
59 int main()
60 {
61     SuperVar A('c'), B(12), C(1.44F);
62     A.print();
63     B.print();
64     C.print();
65
66     return 0;
67 }