Permutation.h

//-----------------------------------------------------------------------------
//
// Module:       Permutation.h
//
// Author:       Feng Xie -- xief@mcmaster.ca
//
// Discription:  Permutation functional object.
//
// Note:         Index starts from 0.
//
// Change log:
//   09-06-02    Created.
//
//-----------------------------------------------------------------------------

#ifndef OMC_PERMUTATION_H
#define OMC_PERMUTATION_H

#include "Core.h"
#include <vector>
#include <algorithm>
#include <iostream>

namespace omc
{
  class Permutation
  {
    friend std::ostream & operator<< (std::ostream &, const Permutation &);

  public:
    Permutation (size_t);                 // constructor
    Permutation (std::vector<index_t> &);          

    index_t & operator[] (index_t);       // operator []
    index_t operator[] (index_t) const;   // can replace operator()

    index_t operator() (index_t) const;   // permuting

    bool next ();                         // generate the next permutation

  protected:
    std::vector <index_t> m_Perm;
  };

  // Output stream overloading.
  std::ostream & operator<< (std::ostream &, const Permutation &); 

  inline Permutation::Permutation (size_t n) {
    for (index_t i=0; i<n; i++) 
      m_Perm.push_back (i);
  }

  inline Permutation::Permutation (std::vector<index_t> & Perm) 
    : m_Perm (Perm)
  {}

  inline index_t & Permutation::operator[] (index_t i) {
    return m_Perm[i];
  }
  
  inline index_t Permutation::operator[] (index_t i) const {
    return m_Perm[i];
  }

  inline index_t Permutation::operator() (index_t i) const {
    if (i >= m_Perm.size())
      throw OMCException ("Index out of bound!", "Permutation::operator()"); 
    return m_Perm[i];
  }

  inline bool Permutation::next () {
    return std::next_permutation (m_Perm.begin(), m_Perm.end());
  }

 
  inline std::ostream & operator<< (std::ostream & os, 
                                    const Permutation & pi) 
  {
    for (index_t i=0; i<pi.m_Perm.size(); i++)
      os << pi.m_Perm[i];
    return os;
  }

} // namespace omc

#endif // OMC_PERMUTATION_H

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