2009-11-04 预处理

2009-11-04 

/*如果defined的参数已经被#define 定义过，那么defined 返回1 否则返回0*/#if defined (IBMPC)#include "ibmpc.h"#elif defined (VAX)#include "vax.h"#elif defined (MAC)#include "mac.h"#else#include "general.h"#endif#include<iostream>using namespace std;int main(void){ char a[]="qqweqweq"; char b[]="asd"; char *q=b; char *p=a; while(*q) { *p++=*q++; } *p='/0'; p=p-strlen(b); cout<<p<<endl;}

/*预处理标识符*/#include<stdio.h>void whyMe();int main(void){printf("The file is %s/n",__FILE__);//当前源代码文件名的字符串文字printf("The date is %s/n",__DATE__);//进行预处理的日期printf("The time is %s/n",__TIME__);//源文件的编译时间printf("This is line %d/n",__LINE__);//当前的行数//printf("This function is %s/n",__func__);//当前函数的名字whyMe();return 0;}void whyMe(void){//printf("This function is %s/n",__func__);printf("THis is line %d/n",__LINE__);}#line 10#line 1000 "cool.c"//把行号和文件重置

 

/**/#include<stdio.h>#include<math.h>#define RAD_TO_DEG (180 / (4 * atan(1)))typedef struct polar_v{double magnitude;double angle;}POLAR_V;typedef struct rect_v{double x;double y;}RECT_V;POLAR_V rect_to_polar(RECT_V);int main(void){RECT_V input;POLAR_V result;puts("Enter x,y ccordinates enter q to quit:");while(scanf("%lf%lf",&input.x, &input.y) == 1){result = rect_to_polar(input);printf("magnitude = %.2f,angle = %.2f/n",result.magnitude, result.angle);}puts("Bye");return 0;}POLAR_V rect_to_polar(RECT_V rv){POLAR_V pv;pv.magnitude = sqrt(rv.x * rv.x +rv.y * rv.y);if(pv.magnitude == 0){pv.angle = 0.0;}else{pv.angle = RAD_TO_DEG * atan2(rv.y,rv.x);}return pv;}