permlib 0.2.9
Library for permutation computations
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bsgs_generator.h
1// ---------------------------------------------------------------------------
2//
3// This file is part of PermLib.
4//
5// Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
6// All rights reserved.
7//
8// Redistribution and use in source and binary forms, with or without
9// modification, are permitted provided that the following conditions
10// are met:
11// 1. Redistributions of source code must retain the above copyright
12// notice, this list of conditions and the following disclaimer.
13// 2. Redistributions in binary form must reproduce the above copyright
14// notice, this list of conditions and the following disclaimer in the
15// documentation and/or other materials provided with the distribution.
16// 3. The name of the author may not be used to endorse or promote products
17// derived from this software without specific prior written permission.
18//
19// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29//
30// ---------------------------------------------------------------------------
31
32
33#ifndef BSGSGENERATOR_H_
34#define BSGSGENERATOR_H_
35
36#include <permlib/common.h>
37#include <permlib/generator/generator.h>
38
39#include <boost/scoped_ptr.hpp>
40
41namespace permlib {
42
44
47template <class TRANS>
48class BSGSGenerator : public Generator<typename TRANS::PERMtype> {
49private:
50 typedef typename TRANS::PERMtype PERM;
51public:
53
56 BSGSGenerator(const std::vector<TRANS>& U);
57 virtual ~BSGSGenerator() {}
58
59 virtual PERM next();
60 virtual bool hasNext();
61private:
62 const std::vector<TRANS>& m_U;
63 std::vector<std::list<unsigned long>::const_iterator > m_Upositions;
64 bool m_hasNext;
65};
66
67//
68// ---- IMPLEMENTATION
69//
70
71template <class TRANS>
72BSGSGenerator<TRANS>::BSGSGenerator(const std::vector<TRANS>& U)
73 : m_U(U), m_Upositions(U.size()), m_hasNext(true)
74{
75 for (unsigned int i = 0; i < m_U.size(); ++i) {
76 m_Upositions[i] = m_U[i].begin();
77 }
78}
79
80
81template <class TRANS>
83 return m_hasNext;
84}
85
86
87template <class TRANS>
88typename BSGSGenerator<TRANS>::PERM BSGSGenerator<TRANS>::next() {
89 BOOST_ASSERT( m_hasNext );
90 PERM g(m_U[0].n());
91 for (int i = m_Upositions.size() - 1; i >= 0; --i) {
92 boost::scoped_ptr<PERM> u_beta( m_U[i].at( *m_Upositions[i] ) );
93 BOOST_ASSERT( u_beta );
94 g *= *u_beta;
95 }
96
97 // advance position
98 int i;
99 for (i = m_Upositions.size() - 1; i >= 0; --i) {
100 m_Upositions[i]++;
101 if (m_Upositions[i] == m_U[i].end())
102 m_Upositions[i] = m_U[i].begin();
103 else
104 break;
105 }
106 if ( i < 0 )
107 m_hasNext = false;
108
109 return g;
110}
111
112}
113
114#endif // -- BSGSGENERATOR_H_
stateful generator of BSGS elements
Definition: bsgs_generator.h:48
virtual PERM next()
generates an element
Definition: bsgs_generator.h:88
virtual bool hasNext()
true, iff more elements can be generated
Definition: bsgs_generator.h:82
BSGSGenerator(const std::vector< TRANS > &U)
constructor
Definition: bsgs_generator.h:72
interface for group element generators
Definition: generator.h:40