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- /*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
- /* __ieee754_atanh(x)
- * Method :
- * 1.Reduced x to positive by atanh(-x) = -atanh(x)
- * 2.For x>=0.5
- * 1 2x x
- * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
- * 2 1 - x 1 - x
- *
- * For x<0.5
- * atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
- *
- * Special cases:
- * atanh(x) is NaN if |x| > 1 with signal;
- * atanh(NaN) is that NaN with no signal;
- * atanh(+-1) is +-INF with signal.
- *
- */
- #include "math.h"
- #include "math_private.h"
- static const double one = 1.0, huge = 1e300;
- static const double zero = 0.0;
- double attribute_hidden __ieee754_atanh(double x)
- {
- double t;
- int32_t hx,ix;
- u_int32_t lx;
- EXTRACT_WORDS(hx,lx,x);
- ix = hx&0x7fffffff;
- if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */
- return (x-x)/(x-x);
- if(ix==0x3ff00000)
- return x/zero;
- if(ix<0x3e300000&&(huge+x)>zero) return x; /* x<2**-28 */
- SET_HIGH_WORD(x,ix);
- if(ix<0x3fe00000) { /* x < 0.5 */
- t = x+x;
- t = 0.5*log1p(t+t*x/(one-x));
- } else
- t = 0.5*log1p((x+x)/(one-x));
- if(hx>=0) return t; else return -t;
- }
- /*
- * wrapper atanh(x)
- */
- #ifndef _IEEE_LIBM
- double atanh(double x)
- {
- double z, y;
- z = __ieee754_atanh(x);
- if (_LIB_VERSION == _IEEE_ || isnan(x))
- return z;
- y = fabs(x);
- if (y >= 1.0) {
- if (y > 1.0)
- return __kernel_standard(x, x, 30); /* atanh(|x|>1) */
- return __kernel_standard(x, x, 31); /* atanh(|x|==1) */
- }
- return z;
- }
- #else
- strong_alias(__ieee754_atanh, atanh)
- #endif
- libm_hidden_def(atanh)
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