C语言简单示例(宏定义一应用)

#include<stdio.h>

#if 0
void swap(int a, int b)
{
char tmp;

tmp = b;
b = a;
a = tmp;
}
#endif

#define SWAP(a, b)   \
do{                  \
char tmp;    \
\
tmp = b;     \
b = a;       \
a = tmp;     \
}while(0)

void reverse(char buf[], int i)
{
int j = 0;

/* string "321" to string "123" */
for(j = 0; j< i/2; j++)
{
if(j >= 0)
SWAP(buf[j],buf[i-1-j]);
else
printf("error\n");
}

}

void itoa(int num, char buf[])
{
int i = 0;

/* num 123 to string "321" */
do
{
buf[i] = num % 10 + '0';
i++;

num /= 10;
}while(num != 0);
buf[i] = '\0';

reverse(buf, i);

return;
}

int main(void)
{
int num = 123;
char buf[10];

printf("input a number\n");
scanf("%d", &num);
printf("numm = %d\n", num);

itoa(num,buf);

printf("2. buf = %s\n", buf);

return 0;
}