external/bsd/pcc/dist/pcc-libs/libF77/tanh.c

   1 /*      $Id: tanh.c,v 1.1.1.1 2008/08/24 05:34:47 gmcgarry Exp $        */
   2 /*
   3  * Copyright(C) Caldera International Inc. 2001-2002. All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * Redistributions of source code and documentation must retain the above
  10  * copyright notice, this list of conditions and the following disclaimer.
  11  * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditionsand the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  * All advertising materials mentioning features or use of this software
  15  * must display the following acknowledgement:
  16  *      This product includes software developed or owned by Caldera
  17  *      International, Inc.
  18  * Neither the name of Caldera International, Inc. nor the names of other
  19  * contributors may be used to endorse or promote products derived from
  20  * this software without specific prior written permission.
  21  *
  22  * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
  23  * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
  24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  25  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26  * DISCLAIMED.  IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OFLIABILITY, WHETHER IN CONTRACT,
  31  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  32  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  33  * POSSIBILITY OF SUCH DAMAGE.
  34  */
  35 /*
  36         tanh(arg) computes the hyperbolic tangent of its floating
  37         point argument.
  38
  39         sinh and cosh are called except for large arguments, which
  40         would cause overflow improperly.
  41 */
  42
  43 double sinh(), cosh();
  44
  45 double
  46 tanh(arg) double arg; {
  47
  48         double sign;
  49
  50         sign = 1.;
  51         if(arg < 0.){
  52                 arg = -arg;
  53                 sign = -1.;
  54         }
  55
  56         if(arg > 21.){
  57                 return(sign);
  58         }
  59
  60         return(sign*sinh(arg)/cosh(arg));
  61 }