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// reverse.h
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Copyright 2005-2010 Google, Inc.
// Author: riley@google.com (Michael Riley)
//
// \file
// Expand a PDT to an FST.
#ifndef FST_EXTENSIONS_PDT_REVERSE_H__
#define FST_EXTENSIONS_PDT_REVERSE_H__
#include <unordered_map>
using std::tr1::unordered_map;
using std::tr1::unordered_multimap;
#include <vector>
using std::vector;
#include <fst/mutable-fst.h>
#include <fst/relabel.h>
#include <fst/reverse.h>
namespace fst {
// Reverses a pushdown transducer (PDT) encoded as an FST.
template<class Arc, class RevArc>
void Reverse(const Fst<Arc> &ifst,
const vector<pair<typename Arc::Label,
typename Arc::Label> > &parens,
MutableFst<RevArc> *ofst) {
typedef typename Arc::Label Label;
// Reverses FST
Reverse(ifst, ofst);
// Exchanges open and close parenthesis pairs
vector<pair<Label, Label> > relabel_pairs;
for (size_t i = 0; i < parens.size(); ++i) {
relabel_pairs.push_back(make_pair(parens[i].first, parens[i].second));
relabel_pairs.push_back(make_pair(parens[i].second, parens[i].first));
}
Relabel(ofst, relabel_pairs, relabel_pairs);
}
} // namespace fst
#endif // FST_EXTENSIONS_PDT_REVERSE_H__
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