学步园

#include <stdio.h></p> <p>#define ISUNSIGNED(a) (a >= 0) && (~a >= 0)<br /> // 如果要考虑整形提升的话<br /> #define ISUNSIGNED_EX(type, a) ((type)a >= (type)0) && ((type)~a >= (type)0) </p> <p>int main()<br /> {<br /> int a = 0;<br /> unsigned char b = 0;<br /> int c = 1;<br /> int d = -1;</p> <p> printf("%d /n", ISUNSIGNED(a));<br /> printf("%d /n", ISUNSIGNED(b));<br /> printf("%d /n", ISUNSIGNED(c));<br /> printf("%d /n", ISUNSIGNED(d));</p> <p> printf("---------/n");</p> <p> printf("%d /n", ISUNSIGNED_EX(short int, a));<br /> printf("%d /n", ISUNSIGNED_EX(unsigned char, b));<br /> printf("%d /n", ISUNSIGNED_EX(int, c));<br /> printf("%d /n", ISUNSIGNED_EX(int, d));</p> <p> return 0;<br /> }</p> <p>输出：<br /> 0<br /> 0<br /> 0<br /> 0<br /> ---------<br /> 0<br /> 1<br /> 0<br /> 0<br /> Press any key to continue  

引用至：求教一个面试题。http://topic.csdn.net/u/20090618/18/b892dbeb-2e2a-43cf-91bd-94ce661ad104.html?18292