1*05a0b428SJohn Marino /* e_acosf.c -- float version of e_acos.c.
2*05a0b428SJohn Marino * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*05a0b428SJohn Marino */
4*05a0b428SJohn Marino
5*05a0b428SJohn Marino /*
6*05a0b428SJohn Marino * ====================================================
7*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*05a0b428SJohn Marino *
9*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
10*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
11*05a0b428SJohn Marino * software is freely granted, provided that this notice
12*05a0b428SJohn Marino * is preserved.
13*05a0b428SJohn Marino * ====================================================
14*05a0b428SJohn Marino */
15*05a0b428SJohn Marino
16*05a0b428SJohn Marino #include "math.h"
17*05a0b428SJohn Marino #include "math_private.h"
18*05a0b428SJohn Marino
19*05a0b428SJohn Marino static const float
20*05a0b428SJohn Marino one = 1.0000000000e+00, /* 0x3F800000 */
21*05a0b428SJohn Marino pi = 3.1415925026e+00, /* 0x40490fda */
22*05a0b428SJohn Marino pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
23*05a0b428SJohn Marino pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
24*05a0b428SJohn Marino pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
25*05a0b428SJohn Marino pS1 = -3.2556581497e-01, /* 0xbea6b090 */
26*05a0b428SJohn Marino pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
27*05a0b428SJohn Marino pS3 = -4.0055535734e-02, /* 0xbd241146 */
28*05a0b428SJohn Marino pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
29*05a0b428SJohn Marino pS5 = 3.4793309169e-05, /* 0x3811ef08 */
30*05a0b428SJohn Marino qS1 = -2.4033949375e+00, /* 0xc019d139 */
31*05a0b428SJohn Marino qS2 = 2.0209457874e+00, /* 0x4001572d */
32*05a0b428SJohn Marino qS3 = -6.8828397989e-01, /* 0xbf303361 */
33*05a0b428SJohn Marino qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
34*05a0b428SJohn Marino
35*05a0b428SJohn Marino float
acosf(float x)36*05a0b428SJohn Marino acosf(float x)
37*05a0b428SJohn Marino {
38*05a0b428SJohn Marino float z,p,q,r,w,s,c,df;
39*05a0b428SJohn Marino int32_t hx,ix;
40*05a0b428SJohn Marino GET_FLOAT_WORD(hx,x);
41*05a0b428SJohn Marino ix = hx&0x7fffffff;
42*05a0b428SJohn Marino if(ix==0x3f800000) { /* |x|==1 */
43*05a0b428SJohn Marino if(hx>0) return 0.0; /* acos(1) = 0 */
44*05a0b428SJohn Marino else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
45*05a0b428SJohn Marino } else if(ix>0x3f800000) { /* |x| >= 1 */
46*05a0b428SJohn Marino return (x-x)/(x-x); /* acos(|x|>1) is NaN */
47*05a0b428SJohn Marino }
48*05a0b428SJohn Marino if(ix<0x3f000000) { /* |x| < 0.5 */
49*05a0b428SJohn Marino if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
50*05a0b428SJohn Marino z = x*x;
51*05a0b428SJohn Marino p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
52*05a0b428SJohn Marino q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
53*05a0b428SJohn Marino r = p/q;
54*05a0b428SJohn Marino return pio2_hi - (x - (pio2_lo-x*r));
55*05a0b428SJohn Marino } else if (hx<0) { /* x < -0.5 */
56*05a0b428SJohn Marino z = (one+x)*(float)0.5;
57*05a0b428SJohn Marino p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
58*05a0b428SJohn Marino q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
59*05a0b428SJohn Marino s = sqrtf(z);
60*05a0b428SJohn Marino r = p/q;
61*05a0b428SJohn Marino w = r*s-pio2_lo;
62*05a0b428SJohn Marino return pi - (float)2.0*(s+w);
63*05a0b428SJohn Marino } else { /* x > 0.5 */
64*05a0b428SJohn Marino int32_t idf;
65*05a0b428SJohn Marino z = (one-x)*(float)0.5;
66*05a0b428SJohn Marino s = sqrtf(z);
67*05a0b428SJohn Marino df = s;
68*05a0b428SJohn Marino GET_FLOAT_WORD(idf,df);
69*05a0b428SJohn Marino SET_FLOAT_WORD(df,idf&0xfffff000);
70*05a0b428SJohn Marino c = (z-df*df)/(s+df);
71*05a0b428SJohn Marino p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
72*05a0b428SJohn Marino q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
73*05a0b428SJohn Marino r = p/q;
74*05a0b428SJohn Marino w = r*s+c;
75*05a0b428SJohn Marino return (float)2.0*(df+w);
76*05a0b428SJohn Marino }
77*05a0b428SJohn Marino }
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