cpp/CPrimerPlus6E/Ch16/rect_pol.c

/* rect_pol.c -- converts rectangular coordinates to polar */
#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 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\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;
}