参数化宏 Defined() 操作符 C库函数 isalnum() 参数化宏 #include <stdio.h> #define MAX(x,y) ((x) > (y) ? (x) : (y)) int main(void) { printf("Max between 20 and 10 is %d\n", MAX(10, 20)); return 0; } Defined() 操作符 C库函数 isalnum()