// See www.openfst.org for extensive documentation on this weighted
|
// finite-state transducer library.
|
//
|
// Expands a PDT to an FST.
|
|
#ifndef FST_EXTENSIONS_PDT_REVERSE_H_
|
#define FST_EXTENSIONS_PDT_REVERSE_H_
|
|
#include <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 std::vector<
|
std::pair<typename Arc::Label, typename Arc::Label>> &parens,
|
MutableFst<RevArc> *ofst) {
|
using Label = typename Arc::Label;
|
// Reverses FST component.
|
Reverse(ifst, ofst);
|
// Exchanges open and close parenthesis pairs.
|
std::vector<std::pair<Label, Label>> relabel_pairs;
|
relabel_pairs.reserve(2 * parens.size());
|
for (const auto &pair : parens) {
|
relabel_pairs.emplace_back(pair.first, pair.second);
|
relabel_pairs.emplace_back(pair.second, pair.first);
|
}
|
Relabel(ofst, relabel_pairs, relabel_pairs);
|
}
|
|
} // namespace fst
|
|
#endif // FST_EXTENSIONS_PDT_REVERSE_H_
|
