* 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 "libm.h"
static const float atanhi[] = {
4.6364760399e-01,
7.8539812565e-01,
9.8279368877e-01,
1.5707962513e+00,
};
static const float atanlo[] = {
5.0121582440e-09,
3.7748947079e-08,
3.4473217170e-08,
7.5497894159e-08,
};
static const float aT[] = {
3.3333328366e-01,
-1.9999158382e-01,
1.4253635705e-01,
-1.0648017377e-01,
6.1687607318e-02,
};
float atanf(float x)
{
float_t w,s1,s2,z;
uint32_t ix,sign;
int id;
GET_FLOAT_WORD(ix, x);
sign = ix>>31;
ix &= 0x7fffffff;
if (ix >= 0x4c800000) {
if (isnan(x))
return x;
z = atanhi[3] + 0x1p-120f;
return sign ? -z : z;
}
if (ix < 0x3ee00000) {
if (ix < 0x39800000) {
if (ix < 0x00800000)
FORCE_EVAL(x*x);
return x;
}
id = -1;
} else {
x = fabsf(x);
if (ix < 0x3f980000) {
if (ix < 0x3f300000) {
id = 0;
x = (2.0f*x - 1.0f)/(2.0f + x);
} else {
id = 1;
x = (x - 1.0f)/(x + 1.0f);
}
} else {
if (ix < 0x401c0000) {
id = 2;
x = (x - 1.5f)/(1.0f + 1.5f*x);
} else {
id = 3;
x = -1.0f/x;
}
}
}
z = x*x;
w = z*z;
s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
s2 = w*(aT[1]+w*aT[3]);
if (id < 0)
return x - x*(s1+s2);
z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
return sign ? -z : z;
}
