1 1.1 mrg /* Support routines for the intrinsic power (**) operator. 2 1.1.1.4 mrg Copyright (C) 2004-2024 Free Software Foundation, Inc. 3 1.1 mrg Contributed by Paul Brook 4 1.1 mrg 5 1.1 mrg This file is part of the GNU Fortran 95 runtime library (libgfortran). 6 1.1 mrg 7 1.1 mrg Libgfortran is free software; you can redistribute it and/or 8 1.1 mrg modify it under the terms of the GNU General Public 9 1.1 mrg License as published by the Free Software Foundation; either 10 1.1 mrg version 3 of the License, or (at your option) any later version. 11 1.1 mrg 12 1.1 mrg Libgfortran is distributed in the hope that it will be useful, 13 1.1 mrg but WITHOUT ANY WARRANTY; without even the implied warranty of 14 1.1 mrg MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 1.1 mrg GNU General Public License for more details. 16 1.1 mrg 17 1.1 mrg Under Section 7 of GPL version 3, you are granted additional 18 1.1 mrg permissions described in the GCC Runtime Library Exception, version 19 1.1 mrg 3.1, as published by the Free Software Foundation. 20 1.1 mrg 21 1.1 mrg You should have received a copy of the GNU General Public License and 22 1.1 mrg a copy of the GCC Runtime Library Exception along with this program; 23 1.1 mrg see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24 1.1 mrg <http://www.gnu.org/licenses/>. */ 25 1.1 mrg 26 1.1 mrg #include "libgfortran.h" 27 1.1 mrg 28 1.1 mrg 29 1.1 mrg /* Use Binary Method to calculate the powi. This is not an optimal but 30 1.1 mrg a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of 31 1.1 mrg Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art 32 1.1 mrg of Computer Programming", 3rd Edition, 1998. */ 33 1.1 mrg 34 1.1 mrg #if defined (HAVE_GFC_REAL_10) && defined (HAVE_GFC_INTEGER_8) 35 1.1 mrg 36 1.1 mrg GFC_REAL_10 pow_r10_i8 (GFC_REAL_10 a, GFC_INTEGER_8 b); 37 1.1 mrg export_proto(pow_r10_i8); 38 1.1 mrg 39 1.1 mrg GFC_REAL_10 40 1.1 mrg pow_r10_i8 (GFC_REAL_10 a, GFC_INTEGER_8 b) 41 1.1 mrg { 42 1.1 mrg GFC_REAL_10 pow, x; 43 1.1 mrg GFC_INTEGER_8 n; 44 1.1 mrg GFC_UINTEGER_8 u; 45 1.1 mrg 46 1.1 mrg n = b; 47 1.1 mrg x = a; 48 1.1 mrg pow = 1; 49 1.1 mrg if (n != 0) 50 1.1 mrg { 51 1.1 mrg if (n < 0) 52 1.1 mrg { 53 1.1 mrg 54 1.1 mrg u = -n; 55 1.1 mrg x = pow / x; 56 1.1 mrg } 57 1.1 mrg else 58 1.1 mrg { 59 1.1 mrg u = n; 60 1.1 mrg } 61 1.1 mrg for (;;) 62 1.1 mrg { 63 1.1 mrg if (u & 1) 64 1.1 mrg pow *= x; 65 1.1 mrg u >>= 1; 66 1.1 mrg if (u) 67 1.1 mrg x *= x; 68 1.1 mrg else 69 1.1 mrg break; 70 1.1 mrg } 71 1.1 mrg } 72 1.1 mrg return pow; 73 1.1 mrg } 74 1.1 mrg 75 1.1 mrg #endif 76
Indexes created Sat Feb 28 05:31:39 UTC 2026