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glibc  2.9
Functions | Variables
e_atan2f.c File Reference
#include "math.h"
#include "math_private.h"

Go to the source code of this file.

Functions

float __ieee754_atan2f (float y, float x)

Variables

static float tiny = 1.0e-30
static float zero = 0.0
static float pi_o_4 = 7.8539818525e-01
static float pi_o_2 = 1.5707963705e+00
static float pi = 3.1415927410e+00
static float pi_lo = -8.7422776573e-08

Function Documentation

float __ieee754_atan2f ( float  y,
float  x 
)

Definition at line 38 of file e_atan2f.c.

{
       float z;
       int32_t k,m,hx,hy,ix,iy;

       GET_FLOAT_WORD(hx,x);
       ix = hx&0x7fffffff;
       GET_FLOAT_WORD(hy,y);
       iy = hy&0x7fffffff;
       if((ix>0x7f800000)||
          (iy>0x7f800000))  /* x or y is NaN */
          return x+y;
       if(hx==0x3f800000) return __atanf(y);   /* x=1.0 */
       m = ((hy>>31)&1)|((hx>>30)&2);     /* 2*sign(x)+sign(y) */

    /* when y = 0 */
       if(iy==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==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;

    /* when x is INF */
       if(ix==0x7f800000) {
           if(iy==0x7f800000) {
              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  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
                  case 3: return (float)-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==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;

    /* compute y/x */
       k = (iy-ix)>>23;
       if(k > 60) z=pi_o_2+(float)0.5*pi_lo;     /* |y/x| >  2**60 */
       else if(hx<0&&k<-60) z=0.0;        /* |y|/x < -2**60 */
       else z=__atanf(fabsf(y/x)); /* safe to do y/x */
       switch (m) {
           case 0: return       z  ;      /* atan(+,+) */
           case 1: {
                    u_int32_t zh;
                    GET_FLOAT_WORD(zh,z);
                    SET_FLOAT_WORD(z,zh ^ 0x80000000);
                  }
                  return       z  ;       /* atan(-,+) */
           case 2: return  pi-(z-pi_lo);/* atan(+,-) */
           default: /* case 3 */
                  return  (z-pi_lo)-pi;/* atan(-,-) */
       }
}

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Variable Documentation

float pi = 3.1415927410e+00 [static]

Definition at line 32 of file e_atan2f.c.

float pi_lo = -8.7422776573e-08 [static]

Definition at line 33 of file e_atan2f.c.

float pi_o_2 = 1.5707963705e+00 [static]

Definition at line 31 of file e_atan2f.c.

float pi_o_4 = 7.8539818525e-01 [static]

Definition at line 30 of file e_atan2f.c.

float tiny = 1.0e-30 [static]

Definition at line 28 of file e_atan2f.c.

float zero = 0.0 [static]

Definition at line 29 of file e_atan2f.c.