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 (at) 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> 25 using std::tr1::unordered_map; 26 using std::tr1::unordered_multimap; 27 #include <vector> 28 using std::vector; 29 30 #include <fst/mutable-fst.h> 31 #include <fst/relabel.h> 32 #include <fst/reverse.h> 33 34 namespace fst { 35 36 // Reverses a pushdown transducer (PDT) encoded as an FST. 37 template<class Arc, class RevArc> 38 void 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
