1/* s_atanf.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#if defined(LIBM_SCCS) && !defined(lint)
17static char rcsid[] = "$NetBSD: s_atanf.c,v 1.4 1995/05/10 20:46:47 jtc Exp $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23#ifdef __STDC__
24static const float atanhi[] = {
25#else
26static float atanhi[] = {
27#endif
28  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
29  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
30  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
31  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
32};
33
34#ifdef __STDC__
35static const float atanlo[] = {
36#else
37static float atanlo[] = {
38#endif
39  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
40  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
41  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
42  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
43};
44
45#ifdef __STDC__
46static const float aT[] = {
47#else
48static float aT[] = {
49#endif
50  3.3333334327e-01, /* 0x3eaaaaaa */
51 -2.0000000298e-01, /* 0xbe4ccccd */
52  1.4285714924e-01, /* 0x3e124925 */
53 -1.1111110449e-01, /* 0xbde38e38 */
54  9.0908870101e-02, /* 0x3dba2e6e */
55 -7.6918758452e-02, /* 0xbd9d8795 */
56  6.6610731184e-02, /* 0x3d886b35 */
57 -5.8335702866e-02, /* 0xbd6ef16b */
58  4.9768779427e-02, /* 0x3d4bda59 */
59 -3.6531571299e-02, /* 0xbd15a221 */
60  1.6285819933e-02, /* 0x3c8569d7 */
61};
62
63#ifdef __STDC__
64	static const float
65#else
66	static float
67#endif
68one   = 1.0,
69huge   = 1.0e30;
70
71#ifdef __STDC__
72	float __atanf(float x)
73#else
74	float __atanf(x)
75	float x;
76#endif
77{
78	float w,s1,s2,z;
79	int32_t ix,hx,id;
80
81	GET_FLOAT_WORD(hx,x);
82	ix = hx&0x7fffffff;
83	if(ix>=0x50800000) {	/* if |x| >= 2^34 */
84	    if(ix>0x7f800000)
85		return x+x;		/* NaN */
86	    if(hx>0) return  atanhi[3]+atanlo[3];
87	    else     return -atanhi[3]-atanlo[3];
88	} if (ix < 0x3ee00000) {	/* |x| < 0.4375 */
89	    if (ix < 0x31000000) {	/* |x| < 2^-29 */
90		if(huge+x>one) return x;	/* raise inexact */
91	    }
92	    id = -1;
93	} else {
94	x = fabsf(x);
95	if (ix < 0x3f980000) {		/* |x| < 1.1875 */
96	    if (ix < 0x3f300000) {	/* 7/16 <=|x|<11/16 */
97		id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
98	    } else {			/* 11/16<=|x|< 19/16 */
99		id = 1; x  = (x-one)/(x+one);
100	    }
101	} else {
102	    if (ix < 0x401c0000) {	/* |x| < 2.4375 */
103		id = 2; x  = (x-(float)1.5)/(one+(float)1.5*x);
104	    } else {			/* 2.4375 <= |x| < 2^66 */
105		id = 3; x  = -(float)1.0/x;
106	    }
107	}}
108    /* end of argument reduction */
109	z = x*x;
110	w = z*z;
111    /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
112	s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
113	s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
114	if (id<0) return x - x*(s1+s2);
115	else {
116	    z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
117	    return (hx<0)? -z:z;
118	}
119}
120weak_alias (__atanf, atanf)
121