1 /* s_atanf.c -- float version of s_atan.c.
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
12 * ====================================================
15 #if defined(LIBM_SCCS) && !defined(lint)
16 static char rcsid
[] = "$NetBSD: s_atanf.c,v 1.4 1995/05/10 20:46:47 jtc Exp $";
21 #include <math_private.h>
22 #include <math-underflow.h>
23 #include <libm-alias-float.h>
25 static const float atanhi
[] = {
26 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
27 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
28 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
29 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
32 static const float atanlo
[] = {
33 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
34 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
35 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
36 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
39 static const float aT
[] = {
40 3.3333334327e-01, /* 0x3eaaaaaa */
41 -2.0000000298e-01, /* 0xbe4ccccd */
42 1.4285714924e-01, /* 0x3e124925 */
43 -1.1111110449e-01, /* 0xbde38e38 */
44 9.0908870101e-02, /* 0x3dba2e6e */
45 -7.6918758452e-02, /* 0xbd9d8795 */
46 6.6610731184e-02, /* 0x3d886b35 */
47 -5.8335702866e-02, /* 0xbd6ef16b */
48 4.9768779427e-02, /* 0x3d4bda59 */
49 -3.6531571299e-02, /* 0xbd15a221 */
50 1.6285819933e-02, /* 0x3c8569d7 */
57 float __atanf(float x
)
64 if(ix
>=0x4c000000) { /* if |x| >= 2^25 */
67 if(hx
>0) return atanhi
[3]+atanlo
[3];
68 else return -atanhi
[3]-atanlo
[3];
69 } if (ix
< 0x3ee00000) { /* |x| < 0.4375 */
70 if (ix
< 0x31000000) { /* |x| < 2^-29 */
71 math_check_force_underflow (x
);
72 if(huge
+x
>one
) return x
; /* raise inexact */
77 if (ix
< 0x3f980000) { /* |x| < 1.1875 */
78 if (ix
< 0x3f300000) { /* 7/16 <=|x|<11/16 */
79 id
= 0; x
= ((float)2.0*x
-one
)/((float)2.0+x
);
80 } else { /* 11/16<=|x|< 19/16 */
81 id
= 1; x
= (x
-one
)/(x
+one
);
84 if (ix
< 0x401c0000) { /* |x| < 2.4375 */
85 id
= 2; x
= (x
-(float)1.5)/(one
+(float)1.5*x
);
86 } else { /* 2.4375 <= |x| < 2^66 */
87 id
= 3; x
= -(float)1.0/x
;
90 /* end of argument reduction */
93 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
94 s1
= z
*(aT
[0]+w
*(aT
[2]+w
*(aT
[4]+w
*(aT
[6]+w
*(aT
[8]+w
*aT
[10])))));
95 s2
= w
*(aT
[1]+w
*(aT
[3]+w
*(aT
[5]+w
*(aT
[7]+w
*aT
[9]))));
96 if (id
<0) return x
- x
*(s1
+s2
);
98 z
= atanhi
[id
] - ((x
*(s1
+s2
) - atanlo
[id
]) - x
);
102 libm_alias_float (__atan
, atan
)