forked from xuos/xiuos
96 lines
2.3 KiB
C
96 lines
2.3 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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* @(#)s_asinh.c 1.3 95/01/18
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*/
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#include "jerry-math-internal.h"
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/* asinh(x)
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* Method :
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* Based on
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* asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
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* we have
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* asinh(x) := x if 1 + x * x = 1,
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* := sign(x) * (log(x)+ln2)) for large |x|, else
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* := sign(x) * log(2|x| + 1 / (|x| + sqrt(x * x + 1))) if|x| > 2, else
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* := sign(x) * log1p(|x| + x^2 / (1 + sqrt(1 + x^2)))
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*/
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#define one 1.0
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#define ln2 6.93147180559945286227e-01 /* 0x3FE62E42, 0xFEFA39EF */
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#define huge 1.0e+300
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double
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asinh (double x)
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{
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double t, w;
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int hx, ix;
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hx = __HI (x);
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ix = hx & 0x7fffffff;
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if (ix >= 0x7ff00000)
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{
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/* x is inf or NaN */
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return x + x;
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}
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if (ix < 0x3e300000)
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{
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/* |x| < 2**-28 */
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if (huge + x > one)
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{
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/* return x inexact except 0 */
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return x;
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}
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}
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if (ix > 0x41b00000)
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{
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/* |x| > 2**28 */
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w = log (fabs (x)) + ln2;
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}
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else if (ix > 0x40000000)
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{
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/* 2**28 > |x| > 2.0 */
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t = fabs (x);
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w = log (2.0 * t + one / (sqrt (x * x + one) + t));
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}
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else
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{
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/* 2.0 > |x| > 2**-28 */
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t = x * x;
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w = log1p (fabs (x) + t / (one + sqrt (one + t)));
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}
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if (hx > 0)
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{
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return w;
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}
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else
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{
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return -w;
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}
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} /* asinh */
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#undef one
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#undef ln2
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#undef huge
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