neighbor.h

一个类似STL的自动机的源代码库

/*
 * ASTL - the Automaton Standard Template Library.
 * C++ generic components for Finite State Automata handling.
 * Copyright (C) 2000-2003 Vincent Le Maout ([e-mail]).
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#ifndef ASTL_NEIGHBOR_H
#define ASTL_NEIGHBOR_H

#include <stack>
#include <vector>
#include <utility>
#include <cursor.h>
#include <iostream>
#include <cstring>   // strlen

using namespace std;

ASTL_BEGIN_NAMESPACE

// Defines:
// neighbor_cursor (forward cursor)

// A neighborood cursor hides the automaton parts straying too far from the
// specified word.

// Instanciation parameters:
// 1. ForwardCursor: a forward cursor type
//
// Requirements:
// None
//
// Constructor: 
// 1. A forward cursor, a word, a max editing distance

// TODO:
// Genericize the distance computing with an object function

template <typename CharType>
struct default_distance : public binary_function<CharType, CharType, int>
{
  int operator()(const CharType& x, const CharType& y) const {
    return x == y ? 0 : 1;
  }
};

template <typename ForwardCursor, typename RandomAccessIterator, 
	  typename DistanceFunction = default_distance<typename ForwardCursor::char_type> >
class neighbor_cursor : public forward_cursor_concept
{
protected:
  ForwardCursor x;
  RandomAccessIterator last; 
  typedef vector<pair<RandomAccessIterator, int> > container; // position, distance 
  container d;    
  static const int INSERTION = 1;
  static const int DELETION = 1;

public:
  typedef neighbor_cursor          self;
  typedef typename ForwardCursor::tag_type    tag_type;
  typedef typename ForwardCursor::char_type   char_type;  
  typedef typename ForwardCursor::char_traits char_traits;
  typedef typename ForwardCursor::state_type  state_type;

  neighbor_cursor(const ForwardCursor& c, RandomAccessIterator i, 
		  RandomAccessIterator j, int dist)
    : x(c), last(j) { 
    d.push_back(make_pair(i, dist));
  }

  neighbor_cursor()
  { }
  
  state_type src() const {
    return x.src();
  }

  bool sink() const {
    return x.sink();
  }

  state_type sink_state() const {
    return x.sink_state();
  }

  bool forward(const char_type &a) {
    typename container::size_type i, j = d.size();
    bool ok = false;

    if (x.forward(a))
      for(i = 0; i < j; ++i) {
	// substitution & deletion
	int dist = d[i].second;
	for(RandomAccessIterator first = d[i].first; 
	    first != last && dist >= 0; 
	    ++first, dist -= DELETION) {
	  int delta = DistanceFunction()(*first, a);
	  if (dist >= delta) {
	    ok = true;
	    d.push_back(make_pair(first + 1, dist - delta));
	  }
	}
	// insertion:
	d[i].second -= INSERTION;
	ok = ok || d[i].second >= 0;
      }
    return ok;
  }

  void forward() {
    typename container::size_type i, j = d.size();

    for(i = 0; i < j; ++i) {
      // substitution & deletion
      int dist = d[i].second;
      for(RandomAccessIterator first = d[i].first; 
	  first != last && dist >= 0; 
	  ++first, dist -= DELETION) {
	int delta = DistanceFunction()(*first, x.letter());
	if (dist >= delta)
	  d.push_back(make_pair(first + 1, dist - delta));
      }
      // insertion:
      d[i].second -= INSERTION;
    }
    x.forward();
  }

  bool src_final() const {
    if (x.src_final())
      for(typename container::const_iterator i = d.begin(); i != d.end(); ++i)
	if (i->second >= (last - i->first) * DELETION) return true;
    return false;
  }
    
  tag_type src_tag() const {
    return x.src_tag();
  }

  bool exists(const char_type &a) const {
    if (x.exists(a)) 
      for(typename container::const_iterator i = d.begin(); i != d.end(); ++i)
	if (i->second >= INSERTION || 
	    (i->first != last && i->second >= DistanceFunction()(*i->first, a))) 
	  return true;

    return false;
  }

  bool operator==(const self &s) const {
    return x == s.x;
  }

  char_type letter() const {
    return x.letter();
  }

  bool first_transition() {
    if (x.first_transition())
      do
	for(typename container::const_iterator i = d.begin(); i != d.end(); ++i)
	  if (i->first != last) {
	    if (i->second >= DistanceFunction()(x.letter(), *i->first)) return true;
	  }
	  else if (i->second >= INSERTION) return true;
      while (x.next_transition());
    return false;
  }
  
  bool next_transition() {
    while (x.next_transition())
      for(typename container::const_iterator i = d.begin(); i != d.end(); ++i)
	if (i->first != last) {
	  if (i->second >= DistanceFunction()(x.letter(), *i->first)) return true;
	}
	else if (i->second >= INSERTION) return true;
    return false;
  }

  bool find(const char_type &a) {
    // TODO
    return false;
  }

  state_type aim() const {
    return x.aim();
  }

  bool aim_final() const {
    self tmp = *this;
    tmp.forward();
    return tmp.src_final();
  }

  tag_type aim_tag() const {
    return x.aim_tag();
  }
};

template <typename ForwardCursor, typename ForwardIterator>
inline
neighbor_cursor<ForwardCursor, ForwardIterator>
neighborc(const ForwardCursor& x, ForwardIterator i, ForwardIterator j, int d) {
  return neighbor_cursor<ForwardCursor, ForwardIterator>(x, i, j, d);
}

template <typename ForwardCursor>
inline
neighbor_cursor<ForwardCursor, const char*>
neighborc(const ForwardCursor& x, const char *word, int d) {
  return neighbor_cursor<ForwardCursor, const char*>(x, word, word + strlen(word), d);
}

ASTL_END_NAMESPACE

#endif