forked from xuos/xiuos
101 lines
2.4 KiB
C
101 lines
2.4 KiB
C
/* Copyright JS Foundation and other contributors, http://js.foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is based on work under the following copyright and permission
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* notice:
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*
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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*
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* @(#)e_atanh.c 1.3 95/01/18
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*/
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#include "jerry-math-internal.h"
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/* atanh(x)
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* Method :
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* 1.Reduced x to positive by atanh(-x) = -atanh(x)
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* 2.For x >= 0.5
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* 1 2x x
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* atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
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* 2 1 - x 1 - x
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*
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* For x < 0.5
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* atanh(x) = 0.5 * log1p(2x + 2x * x / (1 - x))
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*
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* Special cases:
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* atanh(x) is NaN if |x| > 1 with signal;
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* atanh(NaN) is that NaN with no signal;
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* atanh(+-1) is +-INF with signal.
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*
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*/
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#define zero 0.0
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#define one 1.0
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#define huge 1.0e+300
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double
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atanh (double x)
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{
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double t;
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int hx, ix;
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double_accessor temp;
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temp.dbl = x;
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hx = temp.as_int.hi;
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ix = hx & 0x7fffffff;
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/* |x| > 1 */
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if ((ix | ((unsigned int) (temp.as_int.lo | (-temp.as_int.lo)) >> 31)) > 0x3ff00000)
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{
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return NAN;
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}
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if (ix == 0x3ff00000)
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{
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return x / zero;
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}
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if (ix < 0x3e300000 && (huge + x) > zero)
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{
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return x; /* x<2**-28 */
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}
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/* x <- |x| */
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temp.as_int.hi = ix;
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if (ix < 0x3fe00000)
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{
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/* x < 0.5 */
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t = temp.dbl + temp.dbl;
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t = 0.5 * log1p (t + t * temp.dbl / (one - temp.dbl));
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}
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else
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{
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t = 0.5 * log1p ((temp.dbl + temp.dbl) / (one - temp.dbl));
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}
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if (hx >= 0)
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{
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return t;
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}
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else
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{
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return -t;
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}
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} /* atanh */
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#undef zero
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#undef one
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#undef huge
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