#include "math_libm.h"
#include "math_private.h"

Include dependency graph for e_atan2.c:

Functions
double attribute_hidden	__ieee754_atan2 (double y, double x)

Variables
static const double	tiny = 1.0e-300
static const double	zero = 0.0
static const double	pi_o_4 = 7.8539816339744827900E-01
static const double	pi_o_2 = 1.5707963267948965580E+00
static const double	pi = 3.1415926535897931160E+00
static const double	pi_lo = 1.2246467991473531772E-16

Function Documentation

double attribute_hidden __ieee754_atan2	(	double	y,
		double	x
	)

Definition at line 50 of file e_atan2.c.

References atan(), EXTRACT_WORDS, fabs(), GET_HIGH_WORD, k, pi, pi_lo, pi_o_2, pi_o_4, SET_HIGH_WORD, tiny, and zero.

{
        double z;
        int32_t k,m,hx,hy,ix,iy;
        u_int32_t lx,ly;
        EXTRACT_WORDS(hx,lx,x);
        ix = hx&0x7fffffff;
        EXTRACT_WORDS(hy,ly,y);
        iy = hy&0x7fffffff;
        if(((ix|((lx|-(int32_t)lx)>>31))>0x7ff00000)||
           ((iy|((ly|-(int32_t)ly)>>31))>0x7ff00000))   /* x or y is NaN */
           return x+y;
        if(((hx-0x3ff00000)|lx)==0) return atan(y);   /* x=1.0 */
        m = ((hy>>31)&1)|((hx>>30)&2);  /* 2*sign(x)+sign(y) */
    /* when y = 0 */
        if((iy|ly)==0) {
            switch(m) {
                case 0:
                case 1: return y;       /* atan(+-0,+anything)=+-0 */
                case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
                case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
            }
        }
    /* when x = 0 */
        if((ix|lx)==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
    /* when x is INF */
        if(ix==0x7ff00000) {
            if(iy==0x7ff00000) {
                switch(m) {
                    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
                    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
                    case 2: return  3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
                    case 3: return -3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
                }
            } else {
                switch(m) {
                    case 0: return  zero  ;     /* atan(+...,+INF) */
                    case 1: return -zero  ;     /* atan(-...,+INF) */
                    case 2: return  pi+tiny  ;  /* atan(+...,-INF) */
                    case 3: return -pi-tiny  ;  /* atan(-...,-INF) */
                }
            }
        }
    /* when y is INF */
        if(iy==0x7ff00000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
    /* compute y/x */
        k = (iy-ix)>>20;
        if(k > 60) z=pi_o_2+0.5*pi_lo;  /* |y/x| >  2**60 */
        else if(hx<0&&k<-60) z=0.0;     /* |y|/x < -2**60 */
        else z=atan(fabs(y/x));         /* safe to do y/x */
        switch (m) {
            case 0: return       z  ;   /* atan(+,+) */
            case 1: {
                      u_int32_t zh;
                      GET_HIGH_WORD(zh,z);
                      SET_HIGH_WORD(z,zh ^ 0x80000000);
                    }
                    return       z  ;   /* atan(-,+) */
            case 2: return  pi-(z-pi_lo);/* atan(+,-) */
            default: /* case 3 */
                    return  (z-pi_lo)-pi;/* atan(-,-) */
        }
}