1/* Emulation for ldexpl.
2   Contributed by Paolo Bonzini
3
4   Copyright 2002-2003, 2007-2012 Free Software Foundation, Inc.
5
6   This file is part of gnulib.
7
8   This program is free software: you can redistribute it and/or modify
9   it under the terms of the GNU General Public License as published by
10   the Free Software Foundation; either version 3 of the License, or
11   (at your option) any later version.
12
13   This program is distributed in the hope that it will be useful,
14   but WITHOUT ANY WARRANTY; without even the implied warranty of
15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16   GNU General Public License for more details.
17
18   You should have received a copy of the GNU General Public License
19   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
20
21#include <config.h>
22
23/* Specification.  */
24#include <math.h>
25
26#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
27
28long double
29ldexpl (long double x, int exp)
30{
31  return ldexp (x, exp);
32}
33
34#else
35
36# include <float.h>
37# include "fpucw.h"
38
39long double
40ldexpl (long double x, int exp)
41{
42  long double factor;
43  int bit;
44  DECL_LONG_DOUBLE_ROUNDING
45
46  BEGIN_LONG_DOUBLE_ROUNDING ();
47
48  /* Check for zero, nan and infinity. */
49  if (!(isnanl (x) || x + x == x))
50    {
51      if (exp < 0)
52        {
53          exp = -exp;
54          factor = 0.5L;
55        }
56      else
57        factor = 2.0L;
58
59      if (exp > 0)
60        for (bit = 1;;)
61          {
62            /* Invariant: Here bit = 2^i, factor = 2^-2^i or = 2^2^i,
63               and bit <= exp.  */
64            if (exp & bit)
65              x *= factor;
66            bit <<= 1;
67            if (bit > exp)
68              break;
69            factor = factor * factor;
70          }
71    }
72
73  END_LONG_DOUBLE_ROUNDING ();
74
75  return x;
76}
77
78#endif
79
80#if 0
81int
82main (void)
83{
84  long double x;
85  int y;
86  for (y = 0; y < 29; y++)
87    printf ("%5d %.16Lg %.16Lg\n", y, ldexpl (0.8L, y), ldexpl (0.8L, -y) * ldexpl (0.8L, y));
88}
89#endif
90