xref: /third_party/jerryscript/jerry-libm/sinh.c (revision 425bb815) 
1/* Copyright JS Foundation and other contributors, http://js.foundation
2 *
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 *     http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 *
15 * This file is based on work under the following copyright and permission
16 * notice:
17 *
18 *     Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
19 *
20 *     Developed at SunSoft, a Sun Microsystems, Inc. business.
21 *     Permission to use, copy, modify, and distribute this
22 *     software is freely granted, provided that this notice
23 *     is preserved.
24 *
25 *     @(#)e_sinh.c 1.3 95/01/18
26 */
27
28#include "jerry-libm-internal.h"
29
30/* __sinh(x)
31 * Method:
32 * mathematically sinh(x) if defined to be (exp(x) - exp(-x)) / 2
33 *  1. Replace x by |x| (sinh(-x) = -sinh(x)).
34 *  2.
35 *                                             E + E/(E+1)
36 *      0        <= x <= 22     :  sinh(x) := -------------, E = expm1(x)
37 *                                                  2
38 *
39 *      22       <= x <= lnovft :  sinh(x) := exp(x) / 2
40 *      lnovft   <= x <= ln2ovft:  sinh(x) := exp(x / 2) / 2 * exp(x / 2)
41 *      ln2ovft  <  x           :  sinh(x) := x * shuge (overflow)
42 *
43 * Special cases:
44 *  sinh(x) is |x| if x is +INF, -INF, or NaN.
45 *  only sinh(0) = 0 is exact for finite x.
46 */
47
48#define one 1.0
49#define half 0.5
50#define shuge 1.0e307
51
52double
53sinh (double x)
54{
55  double t, w, h;
56  int ix, jx;
57  unsigned lx;
58
59  /* High word of |x|. */
60  jx = __HI (x);
61  ix = jx & 0x7fffffff;
62
63  /* x is INF or NaN */
64  if (ix >= 0x7ff00000)
65  {
66    return x + x;
67  }
68
69  h = 0.5;
70  if (jx < 0)
71  {
72    h = -h;
73  }
74  /* |x| in [0,22], return sign(x) * 0.5 * (E + E / (E + 1))) */
75  if (ix < 0x40360000)
76  {
77    /* |x| < 22 */
78    if (ix < 0x3e300000)
79    {
80      /* |x| < 2**-28 */
81      if (shuge + x > one)
82      {
83        /* sinh(tiny) = tiny with inexact */
84        return x;
85      }
86    }
87    t = expm1 (fabs (x));
88    if (ix < 0x3ff00000)
89    {
90      return h * (2.0 * t - t * t / (t + one));
91    }
92    return h * (t + t / (t + one));
93  }
94
95  /* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */
96  if (ix < 0x40862E42)
97  {
98    return h * exp (fabs (x));
99  }
100  /* |x| in [log(maxdouble), overflowthresold] */
101  lx = ((1 >> 29) + (unsigned int) x);
102  if (ix < 0x408633CE || ((ix == 0x408633ce) && (lx <= (unsigned) 0x8fb9f87d)))
103  {
104    w = exp (0.5 * fabs (x));
105    t = h * w;
106    return t * w;
107  }
108
109  /* |x| > overflowthresold, sinh(x) overflow */
110  return x * shuge;
111} /* sinh */
112
113#undef one
114#undef half
115#undef huge
116