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) == 2)
    {
        result = rect_to_polar(input);
        printf("magnitude = %0.2f, angle = %0.2f
", result.magnitude, result.angle);
    }
    
    return 0;
}

Polar_V rect_to_polar(Rect_V rv)
{
    Polar_V pv;

    pv.magnitude = sqrt(pow(rv.x, 2) + pow(rv.y, 2));
    if (pv.magnitude == 0)
        pv.angle = 0;
    else
        pv.angle = RAD_TO_DEG * atan2(rv.y, rv.x);

    return pv;
}