mirror of
https://github.com/fluencelabs/musl
synced 2025-06-26 21:22:11 +00:00
0cbb654791
zero, one, two, half are replaced by const literals The policy was to use the f suffix for float consts (1.0f), but don't use suffix for long double consts (these consts can be exactly represented as double).
59 lines
1.5 KiB
C
59 lines
1.5 KiB
C
/* origin: FreeBSD /usr/src/lib/msun/src/e_atanh.c */
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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 SunSoft, 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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*/
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/* atanh(x)
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* Method :
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* 1.Reduced x to positive by atanh(-x) = -atanh(x)
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* 2.For x>=0.5
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* 1 2x x
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* atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
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* 2 1 - x 1 - x
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*
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* For x<0.5
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* atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
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*
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* Special cases:
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* atanh(x) is NaN if |x| > 1 with signal;
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* atanh(NaN) is that NaN with no signal;
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* atanh(+-1) is +-INF with signal.
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*
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*/
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#include "libm.h"
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static const double huge = 1e300;
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double atanh(double x)
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{
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double t;
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int32_t hx,ix;
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uint32_t lx;
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EXTRACT_WORDS(hx, lx, x);
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ix = hx & 0x7fffffff;
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if ((ix | ((lx|-lx)>>31)) > 0x3ff00000) /* |x| > 1 */
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return (x-x)/(x-x);
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if (ix == 0x3ff00000)
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return x/0.0;
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if (ix < 0x3e300000 && (huge+x) > 0.0) /* x < 2**-28 */
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return x;
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SET_HIGH_WORD(x, ix);
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if (ix < 0x3fe00000) { /* x < 0.5 */
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t = x+x;
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t = 0.5*log1p(t + t*x/(1.0-x));
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} else
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t = 0.5*log1p((x+x)/(1.0-x));
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if (hx >= 0)
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return t;
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return -t;
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}
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