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diff --git a/math/s_catanhl.c b/math/s_catanhl.c
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+/* Return arc hyperbole tangent for long double value.
+ Copyright (C) 1997, 1998 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
+
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <complex.h>
+#include <math.h>
+
+#include "math_private.h"
+
+
+__complex__ long double
+__catanhl (__complex__ long double x)
+{
+ __complex__ long double res;
+ int rcls = fpclassify (__real__ x);
+ int icls = fpclassify (__imag__ x);
+
+ if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
+ {
+ if (icls == FP_INFINITE)
+ {
+ __real__ res = __copysignl (0.0, __real__ x);
+ __imag__ res = __copysignl (M_PI_2l, __imag__ x);
+ }
+ else if (rcls == FP_INFINITE || rcls == FP_ZERO)
+ {
+ __real__ res = __copysignl (0.0, __real__ x);
+ if (icls >= FP_ZERO)
+ __imag__ res = __copysignl (M_PI_2l, __imag__ x);
+ else
+ __imag__ res = __nanl ("");
+ }
+ else
+ {
+ __real__ res = __nanl ("");
+ __imag__ res = __nanl ("");
+ }
+ }
+ else if (rcls == FP_ZERO && icls == FP_ZERO)
+ {
+ res = x;
+ }
+ else
+ {
+ long double i2, num, den;
+
+ i2 = __imag__ x * __imag__ x;
+
+ num = 1.0 + __real__ x;
+ num = i2 + num * num;
+
+ den = 1.0 - __real__ x;
+ den = i2 + den * den;
+
+ __real__ res = 0.25 * (__ieee754_logl (num) - __ieee754_logl (den));
+
+ den = 1 - __real__ x * __real__ x - i2;
+
+ __imag__ res = 0.5 * __ieee754_atan2l (2.0 * __imag__ x, den);
+ }
+
+ return res;
+}
+weak_alias (__catanhl, catanhl)