Quelle e_acosf.cpp Sprache: C

/* e_acosf.c -- float version of e_acos.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/

/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/

//#include <sys/cdefs.h>
//__FBSDID("$FreeBSD$");

#include "math_private.h"

static const float
one =  1.0000000000e+00, /* 0x3F800000 */
pi =  3.1415925026e+00, /* 0x40490fda */
pio2_hi =  1.5707962513e+00; /* 0x3fc90fda */
static volatile float
pio2_lo =  7.5497894159e-08; /* 0x33a22168 */
static const float
pS0 =  1.6666586697e-01,
pS1 = -4.2743422091e-02,
pS2 = -8.6563630030e-03,
qS1 = -7.0662963390e-01;

float
__ieee754_acosf(float x)
{
float z,p,q,r,w,s,c,df;
int32_t hx,ix;
GET_FLOAT_WORD(hx,x);
ix = hx&0x7fffffff;
if(ix>=0x3f800000) {  /* |x| >= 1 */
     if(ix==0x3f800000) { /* |x| == 1 */
  if(hx>0) return 0.0; /* acos(1) = 0 */
  else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
     }
     return (x-x)/(x-x);  /* acos(|x|>1) is NaN */
}
if(ix<0x3f000000) { /* |x| < 0.5 */
     if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
     z = x*x;
     p = z*(pS0+z*(pS1+z*pS2));
     q = one+z*qS1;
     r = p/q;
     return pio2_hi - (x - (pio2_lo-x*r));
} else  if (hx<0) {  /* x < -0.5 */
     z = (one+x)*(float)0.5;
     p = z*(pS0+z*(pS1+z*pS2));
     q = one+z*qS1;
     s = sqrtf(z);
     r = p/q;
     w = r*s-pio2_lo;
     return pi - (float)2.0*(s+w);
} else {   /* x > 0.5 */
     int32_t idf;
     z = (one-x)*(float)0.5;
     s = sqrtf(z);
     df = s;
     GET_FLOAT_WORD(idf,df);
     SET_FLOAT_WORD(df,idf&0xfffff000);
     c  = (z-df*df)/(s+df);
     p = z*(pS0+z*(pS1+z*pS2));
     q = one+z*qS1;
     r = p/q;
     w = r*s+c;
     return (float)2.0*(df+w);
}
}

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