permlib  0.2.9
Library for permutation computations
symmetric_group_transversal.h
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31 
32 
33 #ifndef SYMMETRIC_GROUP_TRANSVERSAL_H_
34 #define SYMMETRIC_GROUP_TRANSVERSAL_H_
35 
36 #include <boost/iterator/counting_iterator.hpp>
37 
38 namespace permlib {
39 
40 template<class PERM>
41 struct SymmetricGroup;
42 
44 template<class PERM>
46  public:
48 
52  SymmetricGroupTransversal(const SymmetricGroup<PERM>* sg, unsigned int basePos) : symmetricGroup(sg), m_basePos(basePos) {}
53 
55  PERM* at(unsigned long val) const {
56  for (unsigned int i=0; i<m_basePos; ++i) {
57  if ((symmetricGroup->B)[i] == val)
58  return 0;
59  }
60 
61  PERM* p = new PERM(symmetricGroup->B.size());
62  p->setTransposition((symmetricGroup->B)[m_basePos],val);
63  return p;
64  }
65 
67  unsigned int size() const { return symmetricGroup->n - m_basePos; }
68 
69  boost::counting_iterator<unsigned int> begin() const { return boost::counting_iterator<unsigned int>(0); };
70  boost::counting_iterator<unsigned int> end() const { return boost::counting_iterator<unsigned int>(symmetricGroup->n-m_basePos ); };
71  private:
72  const SymmetricGroup<PERM>* symmetricGroup;
73  unsigned int m_basePos;
74 };
75 
76 }
77 
78 #endif // SYMMETRIC_GROUP_TRANSVERSAL_H_
79 
transversal of a symmetric group
Definition: symmetric_group_transversal.h:45
unsigned int size() const
size of basic orbit / transversal
Definition: symmetric_group_transversal.h:67
representation of a symmetric group
Definition: conjugating_base_change.h:45
SymmetricGroupTransversal(const SymmetricGroup< PERM > *sg, unsigned int basePos)
constructs a transversal of a symmetric group
Definition: symmetric_group_transversal.h:52
PERM * at(unsigned long val) const
computes a transversal element on demand if one exists
Definition: symmetric_group_transversal.h:55
Definition: abstract_bsgs.h:49