reverse.h revision f4c12fce1ee58e670f9c3fce46c40296ba9ee8a2
1// reverse.h 2 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15// Copyright 2005-2010 Google, Inc. 16// Author: riley@google.com (Michael Riley) 17// 18// \file 19// Expand a PDT to an FST. 20 21#ifndef FST_EXTENSIONS_PDT_REVERSE_H__ 22#define FST_EXTENSIONS_PDT_REVERSE_H__ 23 24#include <unordered_map> 25using std::tr1::unordered_map; 26using std::tr1::unordered_multimap; 27#include <vector> 28using std::vector; 29 30#include <fst/mutable-fst.h> 31#include <fst/relabel.h> 32#include <fst/reverse.h> 33 34namespace fst { 35 36// Reverses a pushdown transducer (PDT) encoded as an FST. 37template<class Arc, class RevArc> 38void Reverse(const Fst<Arc> &ifst, 39 const vector<pair<typename Arc::Label, 40 typename Arc::Label> > &parens, 41 MutableFst<RevArc> *ofst) { 42 typedef typename Arc::Label Label; 43 44 // Reverses FST 45 Reverse(ifst, ofst); 46 47 // Exchanges open and close parenthesis pairs 48 vector<pair<Label, Label> > relabel_pairs; 49 for (size_t i = 0; i < parens.size(); ++i) { 50 relabel_pairs.push_back(make_pair(parens[i].first, parens[i].second)); 51 relabel_pairs.push_back(make_pair(parens[i].second, parens[i].first)); 52 } 53 Relabel(ofst, relabel_pairs, relabel_pairs); 54} 55 56} // namespace fst 57 58#endif // FST_EXTENSIONS_PDT_REVERSE_H__ 59