1 /* rmint/basic/arith/inv.h - Invert arithmetic functions for rmint 2 3 Copyright Université Joseph Fourier - Grenoble 4 Contributors : 5 Alexis BREUST (alexis.breust@gmail.com 2014) 6 Christophe CHABOT (christophechabotcc@gmail.com 2011) 7 8 9 This software is a computer program whose purpose is to provide an fixed precision arithmetic library. 10 11 This software is governed by the CeCILL-B license under French law and 12 abiding by the rules of distribution of free software. You can use, 13 modify and/ or redistribute the software under the terms of the CeCILL-B 14 license as circulated by CEA, CNRS and INRIA at the following URL 15 "http://www.cecill.info". 16 17 As a counterpart to the access to the source code and rights to copy, 18 modify and redistribute granted by the license, users are provided only 19 with a limited warranty and the software's author, the holder of the 20 economic rights, and the successive licensors have only limited 21 liability. 22 23 In this respect, the user's attention is drawn to the risks associated 24 with loading, using, modifying and/or developing or reproducing the 25 software by the user in light of its specific status of free software, 26 that may mean that it is complicated to manipulate, and that also 27 therefore means that it is reserved for developers and experienced 28 professionals having in-depth computer knowledge. Users are therefore 29 encouraged to load and test the software's suitability as regards their 30 requirements in conditions enabling the security of their systems and/or 31 data to be ensured and, more generally, to use and operate it in the 32 same conditions as regards security. 33 34 The fact that you are presently reading this means that you have had 35 knowledge of the CeCILL-B license and that you accept its terms. 36 */ 37 38 39 #ifndef RMINT_BASIC_ARITH_INV_H 40 #define RMINT_BASIC_ARITH_INV_H 41 42 #include "ruinvmod.h" /* inv_mod() */ 43 #include "rmbrmint.h" 44 #include "rmbreduc.h" 45 46 // -------------------------------------------------------------- 47 // ----------------------- DEFINTIONS --------------------------- 48 49 namespace RecInt 50 { 51 template <size_t K> rmint<K, MGI>& inv(rmint<K, MGI>&, const rmint<K, MGI>&); 52 template <size_t K> rmint<K, MGI>& inv(rmint<K, MGI>&); 53 54 template <size_t K, typename T> __RECINT_IS_ARITH(T, rmint<K, MGI>&) inv(rmint<K, MGI>&, const T&); 55 } 56 57 58 // -------------------------------------------------------------- 59 // --------------------- Implementation ------------------------- 60 61 namespace RecInt 62 { 63 // a = b^(-1) mod a.p or a = 0 if b not invertible 64 template <size_t K> inv(rmint<K,MGI> & a,const rmint<K,MGI> & b)65 inline rmint<K, MGI>& inv(rmint<K, MGI>& a, const rmint<K, MGI>& b) { 66 inv_mod(a.Value, b.Value, a.p); 67 return a; 68 } 69 70 // a = a^(-1) mod a.p or a = 0 if a not invertible 71 template <size_t K> inv(rmint<K,MGI> & a)72 inline rmint<K, MGI>& inv(rmint<K, MGI>& a) { 73 inv_mod(a.Value, a.Value, a.p); 74 return a; 75 } 76 77 // a = b^(-1) mod a.p or a = 0 if b not invertible 78 template <size_t K, typename T> __RECINT_IS_ARITH(T,rmint<K,MGI> &)79 inline __RECINT_IS_ARITH(T, rmint<K, MGI>&) inv(rmint<K, MGI>& a, const T& b) { 80 ruint<K> br(b); 81 inv_mod(a.Value, br, a.p); 82 return a; 83 } 84 } 85 86 #endif 87 88 /* -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ 89 // vim:sts=4:sw=4:ts=4:et:sr:cino=>s,f0,{0,g0,(0,\:0,t0,+0,=s 90