usr/src/lib/libm/common/C/sinh.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  23  */
  24 /*
  25  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28
  29 #pragma weak __sinh = sinh
  30
  31 /* INDENT OFF */
  32 /*
  33  * sinh(x)
  34  * Code originated from 4.3bsd.
  35  * Modified by K.C. Ng for SUN 4.0 libm.
  36  * Method :
  37  *      1. reduce x to non-negative by sinh(-x) = - sinh(x).
  38  *      2.
  39  *
  40  *                                   expm1(x) + expm1(x)/(expm1(x)+1)
  41  *   0 <= x <= lnovft   : sinh(x) := --------------------------------
  42  *                                                                     2
  43  *  lnovft <= x <  INF  : sinh(x) := exp(x-1024*ln2)*2**1023
  44  *
  45  *
  46  * Special cases:
  47  *      sinh(x) is x if x is +INF, -INF, or NaN.
  48  *      only sinh(0)=0 is exact for finite argument.
  49  *
  50  */
  51 /* INDENT ON */
  52
  53 #include "libm.h"
  54
  55 static const double
  56         ln2hi = 6.93147180369123816490e-01,
  57         ln2lo = 1.90821492927058770002e-10,
  58         lnovft = 7.09782712893383973096e+02;
  59
  60 double
  61 sinh(double x) {
  62         double  ox, r, t;
  63
  64         ox = x;
  65         r = fabs(x);
  66         if (!finite(x))
  67                 return (x * r);
  68         if (r < lnovft) {
  69                 t = expm1(r);
  70                 r = copysign((t + t / (1.0 + t)) * 0.5, x);
  71         } else {
  72                 if (r < 1000.0)
  73                         x = copysign(exp((r - 1024 * ln2hi) - 1024 * ln2lo), x);
  74                 r = scalbn(x, 1023);
  75         }
  76         if (!finite(r))
  77                 r = _SVID_libm_err(ox, ox, 25);
  78         return (r);
  79 }