C语言学习 指针的运算和比较

 1 #include <stdio.h>
 2 #include <io_utils.h>
 3 
 4 int main() {
 5   {
 6     int a = 2;
 7     int *p = &a;
 8 
 9     PRINT_INT(p + 1);
10     PRINT_INT(p);
11     PRINT_INT(sizeof(int));
12   }
13 
14   {
15     double a = 2.0;
16     double *p = &a;
17 
18     PRINT_INT(p + 1);
19     PRINT_INT(p);
20     PRINT_INT(sizeof(double ));
21   }
22 
23   {
24     double a = 2.0;
25     double *p = &a;
26     double **pp = &p;
27 
28     PRINT_INT(pp + 1);
29     PRINT_INT(pp);
30     PRINT_INT(sizeof(double *));
31   }
32   {
33     int array[] = {0, 1, 2, 3, 4};
34     PRINT_INT(array);
35     int *p = array;
36     PRINT_INT(*(p + 3));
37     PRINT_INT(*(array + 3));
38     PRINT_INT(*(3 + array));
39     PRINT_INT(3[array]); // not recommend
40     PRINT_INT(array[3]);
41     PRINT_INT(p[3]);
42 
43     int *const array_p = array;
44 
45     PRINT_BOOL(p + 3 > p + 1);
46     PRINT_BOOL(p + 3 == p + 3);
47 
48     int array2[] = {3,4};
49     int *p2 = array2;
50     PRINT_BOOL(p + 3 == p2 + 1); // meaningless
51     PRINT_BOOL(p + 3 > p2 + 1); // meaningless
52   }
53   return 0;
54 }

运行结果

指针比较 是比较连续的地址空间才有意义，要不没有意义。 像50，51 行代码，其实就是没意义的