diff options
Diffstat (limited to 'sysdeps/generic/atanh.c')
| -rw-r--r-- | sysdeps/generic/atanh.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/sysdeps/generic/atanh.c b/sysdeps/generic/atanh.c new file mode 100644 index 0000000000..89cb61cca2 --- /dev/null +++ b/sysdeps/generic/atanh.c @@ -0,0 +1,83 @@ +/* + * 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. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. 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. + */ + +#ifndef lint +static char sccsid[] = "@(#)atanh.c 8.1 (Berkeley) 6/4/93"; +#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) */ + +double atanh(x) +double x; +{ + double z; + z = copysign(0.5,x); + x = copysign(x,1.0); +#if defined(vax)||defined(tahoe) + if (x == 1.0) { + return(copysign(1.0,z)*infnan(ERANGE)); /* sign(x)*INF */ + } +#endif /* defined(vax)||defined(tahoe) */ + x = x/(1.0-x); + return( z*log1p(x+x) ); +} |