/* Support routines for the intrinsic power (**) operator. Copyright 2004 Free Software Foundation, Inc. Contributed by Paul Brook This file is part of the GNU Fortran 95 runtime library (libgfortran). Libgfortran is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. In addition to the permissions in the GNU General Public License, the Free Software Foundation gives you unlimited permission to link the compiled version of this file into combinations with other programs, and to distribute those combinations without any restriction coming from the use of this file. (The General Public License restrictions do apply in other respects; for example, they cover modification of the file, and distribution when not linked into a combine executable.) Libgfortran is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with libgfortran; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "libgfortran.h" /* Use Binary Method to calculate the powi. This is not an optimal but a simple and reasonable arithmetic. See section 4.6.3, "Evaluation of Powers" of Donald E. Knuth, "Seminumerical Algorithms", Vol. 2, "The Art of Computer Programming", 3rd Edition, 1998. */ GFC_COMPLEX_8 pow_c8_i8 (GFC_COMPLEX_8 a, GFC_INTEGER_8 b); export_proto(pow_c8_i8); GFC_COMPLEX_8 pow_c8_i8 (GFC_COMPLEX_8 a, GFC_INTEGER_8 b) { GFC_COMPLEX_8 pow, x; GFC_INTEGER_8 n, u; n = b; x = a; pow = 1; if (n != 0) { if (n < 0) { n = -n; x = pow / x; } u = n; for (;;) { if (u & 1) pow *= x; u >>= 1; if (u) x *= x; else break; } } return pow; }