75 lines
1.8 KiB
C
75 lines
1.8 KiB
C
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/* from: FreeBSD: head/lib/msun/src/e_atanh.c 176451 2008-02-22 02:30:36Z das */
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/* @(#)e_atanh.c 1.3 95/01/18 */
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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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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* See e_atanh.c for complete comments.
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*
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* Converted to long double by David Schultz <das@FreeBSD.ORG> and
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* Bruce D. Evans.
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*/
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#include <float.h>
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#ifdef __i386__
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#include <ieeefp.h>
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#endif
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#include "fpmath.h"
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#include "math.h"
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#include "math_private.h"
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/* EXP_TINY is the threshold below which we use atanh(x) ~= x. */
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#if LDBL_MANT_DIG == 64
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#define EXP_TINY -34
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#elif LDBL_MANT_DIG == 113
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#define EXP_TINY -58
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#else
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#error "Unsupported long double format"
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#endif
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#if LDBL_MAX_EXP != 0x4000
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/* We also require the usual expsign encoding. */
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#error "Unsupported long double format"
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#endif
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#define BIAS (LDBL_MAX_EXP - 1)
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static const double one = 1.0, huge = 1e300;
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static const double zero = 0.0;
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long double
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atanhl(long double x)
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{
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long double t;
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uint16_t hx, ix;
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ENTERI();
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GET_LDBL_EXPSIGN(hx, x);
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ix = hx & 0x7fff;
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if (ix >= 0x3fff) /* |x| >= 1, or NaN or misnormal */
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RETURNI(fabsl(x) == 1 ? x / zero : (x - x) / (x - x));
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if (ix < BIAS + EXP_TINY && (huge + x) > zero)
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RETURNI(x); /* x is tiny */
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SET_LDBL_EXPSIGN(x, ix);
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if (ix < 0x3ffe) { /* |x| < 0.5, or misnormal */
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t = x+x;
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t = 0.5*log1pl(t+t*x/(one-x));
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} else
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t = 0.5*log1pl((x+x)/(one-x));
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RETURNI((hx & 0x8000) == 0 ? t : -t);
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}
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