130 lines
3.1 KiB
C
130 lines
3.1 KiB
C
/* sf_atan.c -- float version of s_atan.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 "fdlibm.h"
|
|
|
|
#ifdef __STDC__
|
|
static const float atanhi[] = {
|
|
#else
|
|
static float atanhi[] = {
|
|
#endif
|
|
4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
|
|
7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
|
|
9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
|
|
1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
|
|
};
|
|
|
|
#ifdef __STDC__
|
|
static const float atanlo[] = {
|
|
#else
|
|
static float atanlo[] = {
|
|
#endif
|
|
5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
|
|
3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
|
|
3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
|
|
7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
|
|
};
|
|
|
|
#ifdef __STDC__
|
|
static const float aT[] = {
|
|
#else
|
|
static float aT[] = {
|
|
#endif
|
|
3.3333334327e-01, /* 0x3eaaaaaa */
|
|
-2.0000000298e-01, /* 0xbe4ccccd */
|
|
1.4285714924e-01, /* 0x3e124925 */
|
|
-1.1111110449e-01, /* 0xbde38e38 */
|
|
9.0908870101e-02, /* 0x3dba2e6e */
|
|
-7.6918758452e-02, /* 0xbd9d8795 */
|
|
6.6610731184e-02, /* 0x3d886b35 */
|
|
-5.8335702866e-02, /* 0xbd6ef16b */
|
|
4.9768779427e-02, /* 0x3d4bda59 */
|
|
-3.6531571299e-02, /* 0xbd15a221 */
|
|
1.6285819933e-02, /* 0x3c8569d7 */
|
|
};
|
|
|
|
#ifdef __STDC__
|
|
static const float
|
|
#else
|
|
static float
|
|
#endif
|
|
one = 1.0,
|
|
huge = 1.0e30;
|
|
|
|
#ifdef __STDC__
|
|
float atanf(float x)
|
|
#else
|
|
float atanf(x)
|
|
float x;
|
|
#endif
|
|
{
|
|
float w,s1,s2,z;
|
|
__int32_t ix,hx,id;
|
|
|
|
GET_FLOAT_WORD(hx,x);
|
|
ix = hx&0x7fffffff;
|
|
if(ix>=0x50800000) { /* if |x| >= 2^34 */
|
|
if(ix>0x7f800000)
|
|
return x+x; /* NaN */
|
|
if(hx>0) return atanhi[3]+atanlo[3];
|
|
else return -atanhi[3]-atanlo[3];
|
|
} if (ix < 0x3ee00000) { /* |x| < 0.4375 */
|
|
if (ix < 0x31000000) { /* |x| < 2^-29 */
|
|
if(huge+x>one) return x; /* raise inexact */
|
|
}
|
|
id = -1;
|
|
} else {
|
|
x = fabsf(x);
|
|
if (ix < 0x3f980000) { /* |x| < 1.1875 */
|
|
if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
|
|
id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
|
|
} else { /* 11/16<=|x|< 19/16 */
|
|
id = 1; x = (x-one)/(x+one);
|
|
}
|
|
} else {
|
|
if (ix < 0x401c0000) { /* |x| < 2.4375 */
|
|
id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
|
|
} else { /* 2.4375 <= |x| < 2^66 */
|
|
id = 3; x = -(float)1.0/x;
|
|
}
|
|
}}
|
|
/* end of argument reduction */
|
|
z = x*x;
|
|
w = z*z;
|
|
/* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
|
|
s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
|
|
s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
|
|
if (id<0) return x - x*(s1+s2);
|
|
else {
|
|
z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
|
|
return (hx<0)? -z:z;
|
|
}
|
|
}
|
|
|
|
#ifdef _DOUBLE_IS_32BITS
|
|
|
|
#ifdef __STDC__
|
|
double atan(double x)
|
|
#else
|
|
double atan(x)
|
|
double x;
|
|
#endif
|
|
{
|
|
return (double) atanf((float) x);
|
|
}
|
|
|
|
#endif /* defined(_DOUBLE_IS_32BITS) */
|