/*      $NetBSD: n_atanhf.c,v 1.1 2016/09/21 14:11:40 christos Exp $ */
/*
* Copyright (c) 1985, 1993
*      The Regents of the University of California.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: n_atanhf.c,v 1.1 2016/09/21 14:11:40 christos Exp $");

#ifndef lint
#if 0
static char sccsid[] = "@(#)atanh.c     8.1 (Berkeley) 6/4/93";
#endif
#endif /* not lint */

/* ATANH(X)
* RETURN THE HYPERBOLIC ARC TANGENT OF X
* DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS)
* CODED IN C BY K.C. NG, 1/8/85;
* REVISED BY K.C. NG on 2/7/85, 3/7/85, 8/18/85.
*
* Required kernel function:
*      log1p(x)        ...return log(1+x)
*
* Method :
*      Return
*                          1              2x                          x
*              atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
*                          2             1 - 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.
*
* Accuracy:
*      atanh(x) returns the exact hyperbolic arc tangent of x nearly rounded.
*      In a test run with 512,000 random arguments on a VAX, the maximum
*      observed error was 1.87 ulps (units in the last place) at
*      x= -3.8962076028810414000e-03.
*/
#include "mathimpl.h"

#if defined(__vax__)||defined(tahoe)
#include <errno.h>
#endif  /* defined(__vax__)||defined(tahoe) */

float
atanhf(float x)
{
       float z;
       z = copysignf(0.5,x);
       x = copysignf(x,1.0);
#if defined(__vax__)||defined(tahoe)
       if (x == 1.0) {
           return(copysignf(1.0,z)*infnan(ERANGE));    /* sign(x)*INF */
       }
#endif  /* defined(__vax__)||defined(tahoe) */
       x = x/(1.0-x);
       return( z*log1pf(x+x) );
}