#define 관련 질문입니다.

#include <stdio.h>
 
static const char *a0 = "hello";
static const char *a1 = "world";
static const char *locl_alpha = NULL;
 
#define alpha get_alpha()
 
void set_alpha(int cond)
{
        if (cond == 0)
                locl_alpha = a0;
        else
                locl_alpha = a1;
}
 
const char *get_alpha(void)
{
        if (!locl_alpha)
                locl_alpha = a0;        /* by default */
 
        return locl_alpha;
}
 
int main(void)
{
        set_alpha(0);
        printf("alpha is %s\n", alpha);
 
        set_alpha(1);
        printf("alpha is %s\n", alpha);
 
        return 0;
}