source: Sophya/trunk/SophyaExt/XephemAstroLib/actan.c@ 3654

#include <math.h>

/* @(#) $Id: actan.c,v 1.8 2009-07-16 10:34:35 cmv Exp $ */

/* commonly in math.h, but not in strict ANSI C */
#ifndef M_PI
#define M_PI            3.14159265358979323846
#define M_PI_2          1.57079632679489661923
#endif

double
actan(double sinx, double cosx)
{
    double ret;

    ret = 0.0;
    if(cosx < 0.0) {
        ret = M_PI;
    } else if(cosx == 0.0) {
        if(sinx < 0.0) {
            return 3.0 * M_PI_2;
        } else if(sinx == 0.0) {
            return ret;
        } else /* sinx > 0.0 */ {
            return M_PI_2;
        }
    } else /* cosx > 0.0 */ {
        if(sinx < 0.0) {
            ret = 2.0 * M_PI;
        } else if(sinx == 0.0) {
            return ret;
        }
    }

    return ret + atan(sinx / cosx);
}


#if 0

#define D(X) (180.0 * (X) / M_PI)

void main() {
    double a, b;

    a =  0.0; b =  2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  1.0; b =  2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  2.0; b =  2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  2.0; b =  1.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  2.0; b =  0.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  2.0; b = -1.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  2.0; b = -2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  1.0; b = -2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a =  0.0; b = -2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -1.0; b = -2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -2.0; b = -2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -2.0; b = -1.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -2.0; b =  0.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -2.0; b =  1.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -2.0; b =  2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
    a = -1.0; b =  2.0; printf("actan(%f, %f) = %f\n", a, b, D(actan(a, b)));
}

#endif /* 0 */

/* For RCS Only -- Do Not Edit */
static char *rcsid[2] = {(char *)rcsid, "@(#) $RCSfile: actan.c,v $ $Date: 2009-07-16 10:34:35 $ $Revision: 1.8 $ $Name: not supported by cvs2svn $"};