1 //===========================================================================
5 // Part of the standard mathematical function library
7 //===========================================================================
8 //####ECOSGPLCOPYRIGHTBEGIN####
9 // -------------------------------------------
10 // This file is part of eCos, the Embedded Configurable Operating System.
11 // Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
13 // eCos is free software; you can redistribute it and/or modify it under
14 // the terms of the GNU General Public License as published by the Free
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17 // eCos is distributed in the hope that it will be useful, but WITHOUT ANY
18 // WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22 // You should have received a copy of the GNU General Public License along
23 // with eCos; if not, write to the Free Software Foundation, Inc.,
24 // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
26 // As a special exception, if other files instantiate templates or use macros
27 // or inline functions from this file, or you compile this file and link it
28 // with other works to produce a work based on this file, this file does not
29 // by itself cause the resulting work to be covered by the GNU General Public
30 // License. However the source code for this file must still be made available
31 // in accordance with section (3) of the GNU General Public License.
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34 // this file might be covered by the GNU General Public License.
36 // Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
37 // at http://sources.redhat.com/ecos/ecos-license/
38 // -------------------------------------------
39 //####ECOSGPLCOPYRIGHTEND####
40 //===========================================================================
41 //#####DESCRIPTIONBEGIN####
43 // Author(s): jlarmour
44 // Contributors: jlarmour
50 //####DESCRIPTIONEND####
52 //===========================================================================
56 #include <pkgconf/libm.h> // Configuration header
58 // Include the Math library?
61 // Derived from code with the following copyright
64 /* @(#)e_atanh.c 1.3 95/01/18 */
66 * ====================================================
67 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
69 * Developed at SunSoft, a Sun Microsystems, Inc. business.
70 * Permission to use, copy, modify, and distribute this
71 * software is freely granted, provided that this notice
73 * ====================================================
79 * 1.Reduced x to positive by atanh(-x) = -atanh(x)
82 * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
86 * atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
89 * atanh(x) is NaN if |x| > 1 with signal;
90 * atanh(NaN) is that NaN with no signal;
91 * atanh(+-1) is +-INF with signal.
95 #include "mathincl/fdlibm.h"
97 static const double one = 1.0, huge = 1e300;
99 static double zero = 0.0;
101 double __ieee754_atanh(double x)
106 hx = CYG_LIBM_HI(x); /* high word */
107 lx = CYG_LIBM_LO(x); /* low word */
109 if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */
113 if(ix<0x3e300000&&(huge+x)>zero) return x; /* x<2**-28 */
114 CYG_LIBM_HI(x) = ix; /* x <- |x| */
115 if(ix<0x3fe00000) { /* x < 0.5 */
117 t = 0.5*log1p(t+t*x/(one-x));
119 t = 0.5*log1p((x+x)/(one-x));
120 if(hx>=0) return t; else return -t;
123 #endif // ifdef CYGPKG_LIBM