111
|
1 /* Support routines for the intrinsic power (**) operator.
|
145
|
2 Copyright (C) 2004-2020 Free Software Foundation, Inc.
|
111
|
3 Contributed by Paul Brook
|
|
4
|
|
5 This file is part of the GNU Fortran 95 runtime library (libgfortran).
|
|
6
|
|
7 Libgfortran is free software; you can redistribute it and/or
|
|
8 modify it under the terms of the GNU General Public
|
|
9 License as published by the Free Software Foundation; either
|
|
10 version 3 of the License, or (at your option) any later version.
|
|
11
|
|
12 Libgfortran is distributed in the hope that it will be useful,
|
|
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
15 GNU General Public License for more details.
|
|
16
|
|
17 Under Section 7 of GPL version 3, you are granted additional
|
|
18 permissions described in the GCC Runtime Library Exception, version
|
|
19 3.1, as published by the Free Software Foundation.
|
|
20
|
|
21 You should have received a copy of the GNU General Public License and
|
|
22 a copy of the GCC Runtime Library Exception along with this program;
|
|
23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
24 <http://www.gnu.org/licenses/>. */
|
|
25
|
|
26 #include "libgfortran.h"
|
|
27
|
|
28
|
|
29 /* Use Binary Method to calculate the powi. This is not an optimal but
|
|
30 a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of
|
|
31 Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art
|
|
32 of Computer Programming", 3rd Edition, 1998. */
|
|
33
|
|
34 #if defined (HAVE_GFC_COMPLEX_8) && defined (HAVE_GFC_INTEGER_8)
|
|
35
|
|
36 GFC_COMPLEX_8 pow_c8_i8 (GFC_COMPLEX_8 a, GFC_INTEGER_8 b);
|
|
37 export_proto(pow_c8_i8);
|
|
38
|
|
39 GFC_COMPLEX_8
|
|
40 pow_c8_i8 (GFC_COMPLEX_8 a, GFC_INTEGER_8 b)
|
|
41 {
|
|
42 GFC_COMPLEX_8 pow, x;
|
|
43 GFC_INTEGER_8 n;
|
|
44 GFC_UINTEGER_8 u;
|
|
45
|
|
46 n = b;
|
|
47 x = a;
|
|
48 pow = 1;
|
|
49 if (n != 0)
|
|
50 {
|
|
51 if (n < 0)
|
|
52 {
|
|
53
|
|
54 u = -n;
|
|
55 x = pow / x;
|
|
56 }
|
|
57 else
|
|
58 {
|
|
59 u = n;
|
|
60 }
|
|
61 for (;;)
|
|
62 {
|
|
63 if (u & 1)
|
|
64 pow *= x;
|
|
65 u >>= 1;
|
|
66 if (u)
|
|
67 x *= x;
|
|
68 else
|
|
69 break;
|
|
70 }
|
|
71 }
|
|
72 return pow;
|
|
73 }
|
|
74
|
|
75 #endif
|