forked from xuos/xiuos
93 lines
2.2 KiB
C
93 lines
2.2 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_acosh.c 1.3 95/01/18
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*/
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#include "jerry-math-internal.h"
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/* acosh(x)
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* Method :
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* Based on
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* acosh(x) = log [ x + sqrt(x * x - 1) ]
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* we have
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* acosh(x) := log(x) + ln2, if x is large; else
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* acosh(x) := log(2x - 1 / (sqrt(x * x - 1) + x)), if x > 2; else
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* acosh(x) := log1p(t + sqrt(2.0 * t + t * t)); where t = x - 1.
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*
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* Special cases:
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* acosh(x) is NaN with signal if x < 1.
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* acosh(NaN) is NaN without signal.
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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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double
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acosh (double x)
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{
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double t;
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int hx;
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hx = __HI (x);
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if (hx < 0x3ff00000)
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{
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/* x < 1 */
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return NAN;
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}
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else if (hx >= 0x41b00000)
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{
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/* x > 2**28 */
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if (hx >= 0x7ff00000)
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{
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/* x is inf of NaN */
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return x + x;
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}
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else
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{
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/* acosh(huge) = log(2x) */
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return log (x) + ln2;
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}
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}
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else if (((hx - 0x3ff00000) | __LO (x)) == 0)
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{
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/* acosh(1) = 0 */
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return 0.0;
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}
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else if (hx > 0x40000000)
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{
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/* 2**28 > x > 2 */
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t = x * x;
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return log (2.0 * x - one / (x + sqrt (t - one)));
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}
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else
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{
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/* 1 < x < 2 */
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t = x - one;
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return log1p (t + sqrt (2.0 * t + t * t));
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}
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} /* acosh */
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#undef one
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#undef ln2
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