permlib  0.2.6
Library for permutation computations
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include/permlib/generator/bsgs_generator.h
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_