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/* e_acosf.c -- float version of e_acos.c. |
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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*/ |
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/* |
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* ==================================================== |
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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* |
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* Developed at SunPro, a Sun Microsystems, Inc. business. |
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* Permission to use, copy, modify, and distribute this |
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* software is freely granted, provided that this notice |
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* is preserved. |
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* ==================================================== |
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*/ |
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#include "math.h" |
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#include "math_private.h" |
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static const float |
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one = 1.0000000000e+00, /* 0x3F800000 */ |
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pi = 3.1415925026e+00, /* 0x40490fda */ |
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pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ |
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pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ |
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pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ |
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pS1 = -3.2556581497e-01, /* 0xbea6b090 */ |
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pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ |
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pS3 = -4.0055535734e-02, /* 0xbd241146 */ |
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pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ |
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pS5 = 3.4793309169e-05, /* 0x3811ef08 */ |
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qS1 = -2.4033949375e+00, /* 0xc019d139 */ |
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qS2 = 2.0209457874e+00, /* 0x4001572d */ |
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qS3 = -6.8828397989e-01, /* 0xbf303361 */ |
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qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ |
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float |
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acosf(float x) |
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{ |
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float z,p,q,r,w,s,c,df; |
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int32_t hx,ix; |
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GET_FLOAT_WORD(hx,x); |
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ix = hx&0x7fffffff; |
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if(ix==0x3f800000) { /* |x|==1 */ |
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if(hx>0) return 0.0; /* acos(1) = 0 */ |
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else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ |
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} else if(ix>0x3f800000) { /* |x| >= 1 */ |
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return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
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} |
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if(ix<0x3f000000) { /* |x| < 0.5 */ |
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if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ |
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z = x*x; |
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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r = p/q; |
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return pio2_hi - (x - (pio2_lo-x*r)); |
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} else if (hx<0) { /* x < -0.5 */ |
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z = (one+x)*(float)0.5; |
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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s = sqrtf(z); |
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r = p/q; |
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w = r*s-pio2_lo; |
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return pi - (float)2.0*(s+w); |
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} else { /* x > 0.5 */ |
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int32_t idf; |
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z = (one-x)*(float)0.5; |
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s = sqrtf(z); |
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df = s; |
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GET_FLOAT_WORD(idf,df); |
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SET_FLOAT_WORD(df,idf&0xfffff000); |
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c = (z-df*df)/(s+df); |
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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r = p/q; |
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w = r*s+c; |
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return (float)2.0*(df+w); |
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} |
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} |