1 /* e_acosf.c -- float version of e_acos.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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
13 * ====================================================
15 * $NetBSD: e_acosf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $
16 * $DragonFly: src/lib/libm/src/e_acosf.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
20 #include "math_private.h"
23 one = 1.0000000000e+00, /* 0x3F800000 */
24 pi = 3.1415925026e+00, /* 0x40490fda */
25 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
26 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
27 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
28 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
29 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
30 pS3 = -4.0055535734e-02, /* 0xbd241146 */
31 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
32 pS5 = 3.4793309169e-05, /* 0x3811ef08 */
33 qS1 = -2.4033949375e+00, /* 0xc019d139 */
34 qS2 = 2.0209457874e+00, /* 0x4001572d */
35 qS3 = -6.8828397989e-01, /* 0xbf303361 */
36 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
41 float z,p,q,r,w,s,c,df;
45 if(ix==0x3f800000) { /* |x|==1 */
46 if(hx>0) return 0.0; /* acos(1) = 0 */
47 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
48 } else if(ix>0x3f800000) { /* |x| >= 1 */
49 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
51 if(ix<0x3f000000) { /* |x| < 0.5 */
52 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
54 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
55 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
57 return pio2_hi - (x - (pio2_lo-x*r));
58 } else if (hx<0) { /* x < -0.5 */
59 z = (one+x)*(float)0.5;
60 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
61 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
65 return pi - (float)2.0*(s+w);
66 } else { /* x > 0.5 */
68 z = (one-x)*(float)0.5;
71 GET_FLOAT_WORD(idf,df);
72 SET_FLOAT_WORD(df,idf&0xfffff000);
74 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
75 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
78 return (float)2.0*(df+w);