Subversion Repositories planix.SVN

#include <math.h>
#include <errno.h>
/*
        atan2 discovers what quadrant the angle
        is in and calls atan.
*/
#define pio2 1.5707963267948966192313217
#define pi   3.1415926535897932384626434;

double
atan2(double arg1, double arg2)
{

        if(arg1 == 0.0 && arg2 == 0.0){
                errno = EDOM;
                return 0.0;
        }
        if(arg1+arg2 == arg1) {
                if(arg1 >= 0)
                        return pio2;
                return -pio2;
        }
        arg1 = atan(arg1/arg2);
        if(arg2 < 0) {
                if(arg1 <= 0)
                        return arg1 + pi;
                return arg1 - pi;
        }
        return arg1;
}