permlib
0.2.6
Library for permutation computations
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00001 // --------------------------------------------------------------------------- 00002 // 00003 // This file is part of PermLib. 00004 // 00005 // Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de> 00006 // All rights reserved. 00007 // 00008 // Redistribution and use in source and binary forms, with or without 00009 // modification, are permitted provided that the following conditions 00010 // are met: 00011 // 1. Redistributions of source code must retain the above copyright 00012 // notice, this list of conditions and the following disclaimer. 00013 // 2. Redistributions in binary form must reproduce the above copyright 00014 // notice, this list of conditions and the following disclaimer in the 00015 // documentation and/or other materials provided with the distribution. 00016 // 3. The name of the author may not be used to endorse or promote products 00017 // derived from this software without specific prior written permission. 00018 // 00019 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 00020 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 00021 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 00022 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 00023 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 00024 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 00025 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 00026 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 00027 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 00028 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 00029 // 00030 // --------------------------------------------------------------------------- 00031 00032 00033 #ifndef BSGSGENERATOR_H_ 00034 #define BSGSGENERATOR_H_ 00035 00036 #include <permlib/common.h> 00037 #include <permlib/generator/generator.h> 00038 00039 #include <boost/scoped_ptr.hpp> 00040 00041 namespace permlib { 00042 00044 00047 template <class TRANS> 00048 class BSGSGenerator : public Generator<typename TRANS::PERMtype> { 00049 private: 00050 typedef typename TRANS::PERMtype PERM; 00051 public: 00053 00056 BSGSGenerator(const std::vector<TRANS>& U); 00057 virtual ~BSGSGenerator() {} 00058 00059 virtual PERM next(); 00060 virtual bool hasNext(); 00061 private: 00062 const std::vector<TRANS>& m_U; 00063 std::vector<std::list<unsigned long>::const_iterator > m_Upositions; 00064 bool m_hasNext; 00065 }; 00066 00067 // 00068 // ---- IMPLEMENTATION 00069 // 00070 00071 template <class TRANS> 00072 BSGSGenerator<TRANS>::BSGSGenerator(const std::vector<TRANS>& U) 00073 : m_U(U), m_Upositions(U.size()), m_hasNext(true) 00074 { 00075 for (unsigned int i = 0; i < m_U.size(); ++i) { 00076 m_Upositions[i] = m_U[i].begin(); 00077 } 00078 } 00079 00080 00081 template <class TRANS> 00082 bool BSGSGenerator<TRANS>::hasNext() { 00083 return m_hasNext; 00084 } 00085 00086 00087 template <class TRANS> 00088 typename BSGSGenerator<TRANS>::PERM BSGSGenerator<TRANS>::next() { 00089 BOOST_ASSERT( m_hasNext ); 00090 PERM g(m_U[0].n()); 00091 for (int i = m_Upositions.size() - 1; i >= 0; --i) { 00092 boost::scoped_ptr<PERM> u_beta( m_U[i].at( *m_Upositions[i] ) ); 00093 BOOST_ASSERT( u_beta ); 00094 g *= *u_beta; 00095 } 00096 00097 // advance position 00098 int i; 00099 for (i = m_Upositions.size() - 1; i >= 0; --i) { 00100 m_Upositions[i]++; 00101 if (m_Upositions[i] == m_U[i].end()) 00102 m_Upositions[i] = m_U[i].begin(); 00103 else 00104 break; 00105 } 00106 if ( i < 0 ) 00107 m_hasNext = false; 00108 00109 return g; 00110 } 00111 00112 } 00113 00114 #endif // -- BSGSGENERATOR_H_