第 16 章 C 预处理器和 C 库（直角坐标转换极坐标）

 /*-------------------------------------
     rect_pol.c -- 把直角坐标转换为极坐标
 -------------------------------------*/

 #include <stdio.h>
 #include <math.h>

 #define RAD_TO_DEG    (180 / (4 * atan(1.0)))

 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()
 {
     Rect_V input;
     Polar_V result;

     puts("Enter x and y coordinates; enter q to quit:");
     while (scanf("%lf %lf", &input.x, &input.y) == )
     {
         result = rect_to_polar(input);
         printf("magnitude = %0.2f, angle = %0.2f\n", result.magnitude, result.angle);
     }

     return ;
 }

 Polar_V rect_to_polar(Rect_V rv)
 {
     Polar_V pv;

     pv.magnitude = sqrt(pow(rv.x, ) + pow(rv.y, ));
     if (pv.magnitude == )
         pv.angle = ;
     else
         pv.angle = RAD_TO_DEG * atan2(rv.y, rv.x);

     return pv;
 }

rect_pol.c