1/* sf_atan.c -- float version of s_atan.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 *
15 */
16
17#include "fdlibm.h"
18
19#ifdef __STDC__
20static const float atanhi[] = {
21#else
22static float atanhi[] = {
23#endif
24  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
25  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
26  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
27  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
28};
29
30#ifdef __STDC__
31static const float atanlo[] = {
32#else
33static float atanlo[] = {
34#endif
35  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
36  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
37  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
38  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
39};
40
41#ifdef __STDC__
42static const float aT[] = {
43#else
44static float aT[] = {
45#endif
46  3.3333334327e-01, /* 0x3eaaaaaa */
47 -2.0000000298e-01, /* 0xbe4ccccd */
48  1.4285714924e-01, /* 0x3e124925 */
49 -1.1111110449e-01, /* 0xbde38e38 */
50  9.0908870101e-02, /* 0x3dba2e6e */
51 -7.6918758452e-02, /* 0xbd9d8795 */
52  6.6610731184e-02, /* 0x3d886b35 */
53 -5.8335702866e-02, /* 0xbd6ef16b */
54  4.9768779427e-02, /* 0x3d4bda59 */
55 -3.6531571299e-02, /* 0xbd15a221 */
56  1.6285819933e-02, /* 0x3c8569d7 */
57};
58
59#ifdef __STDC__
60	static const float
61#else
62	static float
63#endif
64one   = 1.0,
65huge   = 1.0e30;
66
67#ifdef __STDC__
68	float atanf(float x)
69#else
70	float atanf(x)
71	float x;
72#endif
73{
74	float w,s1,s2,z;
75	__int32_t ix,hx,id;
76
77	GET_FLOAT_WORD(hx,x);
78	ix = hx&0x7fffffff;
79	if(ix>=0x50800000) {	/* if |x| >= 2^34 */
80	    if(FLT_UWORD_IS_NAN(ix))
81		return x+x;		/* NaN */
82	    if(hx>0) return  atanhi[3]+atanlo[3];
83	    else     return -atanhi[3]-atanlo[3];
84	} if (ix < 0x3ee00000) {	/* |x| < 0.4375 */
85	    if (ix < 0x31000000) {	/* |x| < 2^-29 */
86		if(huge+x>one) return x;	/* raise inexact */
87	    }
88	    id = -1;
89	} else {
90	x = fabsf(x);
91	if (ix < 0x3f980000) {		/* |x| < 1.1875 */
92	    if (ix < 0x3f300000) {	/* 7/16 <=|x|<11/16 */
93		id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
94	    } else {			/* 11/16<=|x|< 19/16 */
95		id = 1; x  = (x-one)/(x+one);
96	    }
97	} else {
98	    if (ix < 0x401c0000) {	/* |x| < 2.4375 */
99		id = 2; x  = (x-(float)1.5)/(one+(float)1.5*x);
100	    } else {			/* 2.4375 <= |x| < 2^66 */
101		id = 3; x  = -(float)1.0/x;
102	    }
103	}}
104    /* end of argument reduction */
105	z = x*x;
106	w = z*z;
107    /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
108	s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
109	s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
110	if (id<0) return x - x*(s1+s2);
111	else {
112	    z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
113	    return (hx<0)? -z:z;
114	}
115}
116
117#ifdef _DOUBLE_IS_32BITS
118
119#ifdef __STDC__
120	double atan(double x)
121#else
122	double atan(x)
123	double x;
124#endif
125{
126	return (double) atanf((float) x);
127}
128
129#endif /* defined(_DOUBLE_IS_32BITS) */
130