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

Go to the source code of this file.

Functions

float __kernel_tanf (float x, float y, int iy)

Variables

static float one = 1.0000000000e+00
static float pio4 = 7.8539812565e-01
static float pio4lo = 3.7748947079e-08
static float T []

Function Documentation

float __kernel_tanf ( float  x,
float  y,
int  iy 
)

Definition at line 49 of file k_tanf.c.

{
       float z,r,v,w,s;
       int32_t ix,hx;
       GET_FLOAT_WORD(hx,x);
       ix = hx&0x7fffffff;  /* high word of |x| */
       if(ix<0x31800000)                  /* x < 2**-28 */
           {if((int)x==0) {               /* generate inexact */
              if((ix|(iy+1))==0) return one/fabsf(x);
              else return (iy==1)? x: -one/x;
           }
           }
       if(ix>=0x3f2ca140) {                      /* |x|>=0.6744 */
           if(hx<0) {x = -x; y = -y;}
           z = pio4-x;
           w = pio4lo-y;
           x = z+w; y = 0.0;
       }
       z      =  x*x;
       w      =  z*z;
    /* Break x^5*(T[1]+x^2*T[2]+...) into
     *   x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
     *   x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
     */
       r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
       v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
       s = z*x;
       r = y + z*(s*(r+v)+y);
       r += T[0]*s;
       w = x+r;
       if(ix>=0x3f2ca140) {
           v = (float)iy;
           return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
       }
       if(iy==1) return w;
       else {        /* if allow error up to 2 ulp, 
                        simply return -1.0/(x+r) here */
     /*  compute -1.0/(x+r) accurately */
           float a,t;
           int32_t i;
           z  = w;
           GET_FLOAT_WORD(i,z);
           SET_FLOAT_WORD(z,i&0xfffff000);
           v  = r-(z - x);  /* z+v = r+x */
           t = a  = -(float)1.0/w; /* a = -1.0/w */
           GET_FLOAT_WORD(i,t);
           SET_FLOAT_WORD(t,i&0xfffff000);
           s  = (float)1.0+t*z;
           return t+a*(s+t*v);
       }
}

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Variable Documentation

float one = 1.0000000000e+00 [static]

Definition at line 27 of file k_tanf.c.

float pio4 = 7.8539812565e-01 [static]

Definition at line 28 of file k_tanf.c.

float pio4lo = 3.7748947079e-08 [static]

Definition at line 29 of file k_tanf.c.

float T[] [static]
Initial value:
  {
  3.3333334327e-01, 
  1.3333334029e-01, 
  5.3968254477e-02, 
  2.1869488060e-02, 
  8.8632395491e-03, 
  3.5920790397e-03, 
  1.4562094584e-03, 
  5.8804126456e-04, 
  2.4646313977e-04, 
  7.8179444245e-05, 
  7.1407252108e-05, 
 -1.8558637748e-05, 
  2.5907305826e-05, 
}

Definition at line 30 of file k_tanf.c.