指针算术运算(指针 +- 数字,指针 - 指针)
2018-04-07 12:10
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指针 +- 数字 // 需要调整,调整的权重为sizeof(指针只去掉一个*)
指针+1:加一个单元格
首先要清楚占用字节数
char 1
short 2
int 4
long 4
long long 8
float 4
double 8
指针 - 指针 // 间隔的单元(非字节数)个数
步骤:
算出字节数
除以调整的权重
指针+1:加一个单元格
首先要清楚占用字节数
char 1
short 2
int 4
long 4
long long 8
float 4
double 8
int main() { int *p = (int *) //赋值2000(强行转换) printf("%d\n",p+4); //2016 printf("%d\n",(short *)p+4); //2008 printf("%d\n",(double *)p+4); //2032 printf("%d\n",(float **)p+4); //2016 printf("%d\n",(unsigned short *)p+4); //2008 printf("%d\n",(long *)p+4); //2016 printf("%d\n",(char *)p+4); //2004 printf("%d\n",(unsigned long long)p+4); //2004 return 0; }指针+指针不成立,指针 - 指针成立
指针 - 指针 // 间隔的单元(非字节数)个数
步骤:
算出字节数
除以调整的权重
int main() { int arr[10] = {1}; int *p = &arr[1]; //x+4 int *q = &arr[9]; //x+36 printf("%d\n",p-q); //-8 printf("%d\n",q-p); //8 printf("%d\n",(short *)q-(short *)p); //16 printf("%d\n",(double *)q-(double *)p); //4 printf("%d\n",(int ***)q-(int ***)p); //8 printf("%d\n",(char **)q-(char **)p); //8 printf("%d\n",(long)q-(long)p); //32 return 0; }总结:指针的所有算数运算都需要调整,调整的权重为sizeof(指针只去掉一个*)
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