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Diffstat (limited to 'REORG.TODO/sysdeps/ieee754/dbl-64/e_atanh.c')
-rw-r--r-- | REORG.TODO/sysdeps/ieee754/dbl-64/e_atanh.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/ieee754/dbl-64/e_atanh.c b/REORG.TODO/sysdeps/ieee754/dbl-64/e_atanh.c new file mode 100644 index 0000000000..a9d19a0472 --- /dev/null +++ b/REORG.TODO/sysdeps/ieee754/dbl-64/e_atanh.c @@ -0,0 +1,74 @@ +/* Copyright (C) 2011-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@gmail.com>, 2011. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + + +/* __ieee754_atanh(x) + Method : + 1.Reduced x to positive by atanh(-x) = -atanh(x) + 2.For x>=0.5 + 1 2x x + atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) + 2 1 - x 1 - x + + For x<0.5 + atanh(x) = 0.5*log1p(2x+2x*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. + + */ + +#include <float.h> +#include <inttypes.h> +#include <math.h> +#include <math_private.h> + +static const double huge = 1e300; + +double +__ieee754_atanh (double x) +{ + double xa = fabs (x); + double t; + if (isless (xa, 0.5)) + { + if (__glibc_unlikely (xa < 0x1.0p-28)) + { + math_force_eval (huge + x); + math_check_force_underflow (x); + return x; + } + + t = xa + xa; + t = 0.5 * __log1p (t + t * xa / (1.0 - xa)); + } + else if (__glibc_likely (isless (xa, 1.0))) + t = 0.5 * __log1p ((xa + xa) / (1.0 - xa)); + else + { + if (isgreater (xa, 1.0)) + return (x - x) / (x - x); + + return x / 0.0; + } + + return __copysign (t, x); +} +strong_alias (__ieee754_atanh, __atanh_finite) |