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
15 // Software Foundation; either version 2 or (at your option) any later version.
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.
33 // This exception does not invalidate any other reasons why a work based on
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_acosh.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 * ====================================================
80 * acosh(x) = log [ x + sqrt(x*x-1) ]
82 * acosh(x) := log(x)+ln2, if x is large; else
83 * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
84 * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
87 * acosh(x) is NaN with signal if x<1.
88 * acosh(NaN) is NaN without signal.
91 #include "mathincl/fdlibm.h"
95 ln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */
97 double __ieee754_acosh(double x)
102 if(hx<0x3ff00000) { /* x < 1 */
104 } else if(hx >=0x41b00000) { /* x > 2**28 */
105 if(hx >=0x7ff00000) { /* x is inf of NaN */
108 return __ieee754_log(x)+ln2; /* acosh(huge)=log(2x) */
109 } else if(((hx-0x3ff00000)|CYG_LIBM_LO(x))==0) {
110 return 0.0; /* acosh(1) = 0 */
111 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
113 return __ieee754_log(2.0*x-one/(x+sqrt(t-one)));
116 return log1p(t+sqrt(2.0*t+t*t));
120 #endif // ifdef CYGPKG_LIBM