forked from xuos/xiuos
114 lines
3.0 KiB
C
114 lines
3.0 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_cosh.c 1.3 95/01/18
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*/
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#include "jerry-math-internal.h"
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/* cosh(x)
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* Method:
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* mathematically cosh(x) if defined to be (exp(x) + exp(-x)) / 2
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* 1. Replace x by |x| (cosh(x) = cosh(-x)).
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* 2.
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* [ exp(x) - 1 ]^2
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* 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
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* 2*exp(x)
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*
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* exp(x) + 1/exp(x)
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* ln2/2 <= x <= 22 : cosh(x) := -------------------
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* 2
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*
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* 22 <= x <= lnovft : cosh(x) := exp(x)/2
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* lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
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* ln2ovft < x : cosh(x) := huge * huge (overflow)
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*
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* Special cases:
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* cosh(x) is |x| if x is +INF, -INF, or NaN.
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* only cosh(0) = 1 is exact for finite x.
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*/
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#define one 1.0
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#define half 0.5
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#define huge 1.0e300
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double
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cosh (double x)
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{
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double t, w;
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int ix;
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unsigned lx;
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/* High word of |x|. */
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ix = __HI (x);
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ix &= 0x7fffffff;
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/* x is INF or NaN */
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if (ix >= 0x7ff00000)
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{
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return x * x;
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}
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/* |x| in [0, 0.5 * ln2], return 1 + expm1(|x|)^2 / (2 * exp(|x|)) */
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if (ix < 0x3fd62e43)
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{
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t = expm1 (fabs (x));
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w = one + t;
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if (ix < 0x3c800000)
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{
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/* cosh(tiny) = 1 */
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return w;
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}
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return one + (t * t) / (w + w);
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}
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/* |x| in [0.5 * ln2, 22], return (exp(|x|) + 1 / exp(|x|) / 2; */
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if (ix < 0x40360000)
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{
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t = exp (fabs (x));
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return half * t + half / t;
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}
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/* |x| in [22, log(maxdouble)] return half * exp(|x|) */
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if (ix < 0x40862E42)
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{
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return half * exp (fabs (x));
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}
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/* |x| in [log(maxdouble), overflowthresold] */
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lx = ((1 >> 29) + (unsigned int) x);
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if ((ix < 0x408633CE) ||
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((ix == 0x408633ce) && (lx <= (unsigned) 0x8fb9f87d)))
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{
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w = exp (half * fabs (x));
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t = half * w;
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return t * w;
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}
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/* |x| > overflowthresold, cosh(x) overflow */
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return huge * huge;
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} /* cosh */
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#undef one
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#undef half
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#undef huge
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