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

Go to the source code of this file.

Functions

double __kernel_tan (double x, double y, int iy)

Variables

static double one = 1.00000000000000000000e+00
static double pio4 = 7.85398163397448278999e-01
static double pio4lo = 3.06161699786838301793e-17
static double T []

Function Documentation

double __kernel_tan ( double  x,
double  y,
int  iy 
)

Definition at line 83 of file k_tan.c.

{
       double z,r,v,w,s,r1,r2,r3,v1,v2,v3,w2,w4;
       int32_t ix,hx;
       GET_HIGH_WORD(hx,x);
       ix = hx&0x7fffffff;  /* high word of |x| */
       if(ix<0x3e300000)                  /* x < 2**-28 */
           {if((int)x==0) {               /* generate inexact */
               u_int32_t low;
              GET_LOW_WORD(low,x);
              if(((ix|low)|(iy+1))==0) return one/fabs(x);
              else return (iy==1)? x: -one/x;
           }
           }
       if(ix>=0x3FE59428) {                      /* |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]))
     */
#ifdef DO_NOT_USE_THIS
       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])))));
#else
       v1 = T[10]+w*T[12]; w2=w*w;
       v2 = T[6]+w*T[8]; w4=w2*w2;
       v3 = T[2]+w*T[4]; v1=z*v1;
       r1 = T[9]+w*T[11]; v2=z*v2;
       r2 = T[5]+w*T[7]; v3=z*v3;
       r3 = T[1]+w*T[3];
       v  = v3 + w2*v2 + w4*v1;
       r = r3 + w2*r2 + w4*r1;
#endif
       s = z*x;
       r = y + z*(s*(r+v)+y);
       r += T[0]*s;
       w = x+r;
       if(ix>=0x3FE59428) {
           v = (double)iy;
           return (double)(1-((hx>>30)&2))*(v-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 */
           double a,t;
           z  = w;
           SET_LOW_WORD(z,0);
           v  = r-(z - x);  /* z+v = r+x */
           t = a  = -1.0/w; /* a = -1.0/w */
           SET_LOW_WORD(t,0);
           s  = 1.0+t*z;
           return t+a*(s+t*v);
       }
}

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Variable Documentation

double one = 1.00000000000000000000e+00 [static]

Definition at line 61 of file k_tan.c.

double pio4 = 7.85398163397448278999e-01 [static]

Definition at line 62 of file k_tan.c.

double pio4lo = 3.06161699786838301793e-17 [static]

Definition at line 63 of file k_tan.c.

double T[] [static]
Initial value:
  {
  3.33333333333334091986e-01, 
  1.33333333333201242699e-01, 
  5.39682539762260521377e-02, 
  2.18694882948595424599e-02, 
  8.86323982359930005737e-03, 
  3.59207910759131235356e-03, 
  1.45620945432529025516e-03, 
  5.88041240820264096874e-04, 
  2.46463134818469906812e-04, 
  7.81794442939557092300e-05, 
  7.14072491382608190305e-05, 
 -1.85586374855275456654e-05, 
  2.59073051863633712884e-05, 
}

Definition at line 64 of file k_tan.c.