replace.h
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// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
#ifndef FST_SCRIPT_REPLACE_H_
#define FST_SCRIPT_REPLACE_H_
#include <tuple>
#include <utility>
#include <vector>
#include <fst/replace.h>
#include <fst/script/fst-class.h>
namespace fst {
namespace script {
struct ReplaceOptions {
const int64 root; // Root rule for expansion.
const ReplaceLabelType call_label_type; // How to label call arc.
const ReplaceLabelType return_label_type; // How to label return arc.
const int64 return_label; // Specifies return arc label.
explicit ReplaceOptions(int64 root,
ReplaceLabelType call_label_type = REPLACE_LABEL_INPUT,
ReplaceLabelType return_label_type = REPLACE_LABEL_NEITHER,
int64 return_label = 0)
: root(root),
call_label_type(call_label_type),
return_label_type(return_label_type),
return_label(return_label) {}
};
using LabelFstClassPair = std::pair<int64, const FstClass *>;
using ReplaceArgs = std::tuple<const std::vector<LabelFstClassPair> &,
MutableFstClass *, const ReplaceOptions &>;
template <class Arc>
void Replace(ReplaceArgs *args) {
using LabelFstPair = std::pair<typename Arc::Label, const Fst<Arc> *>;
// Now that we know the arc type, we construct a vector of
// std::pair<real label, real fst> that the real Replace will use.
const auto &untyped_pairs = std::get<0>(*args);
std::vector<LabelFstPair> typed_pairs;
typed_pairs.reserve(untyped_pairs.size());
for (const auto &untyped_pair : untyped_pairs) {
typed_pairs.emplace_back(untyped_pair.first, // Converts label.
untyped_pair.second->GetFst<Arc>());
}
MutableFst<Arc> *ofst = std::get<1>(*args)->GetMutableFst<Arc>();
const auto &opts = std::get<2>(*args);
ReplaceFstOptions<Arc> typed_opts(opts.root, opts.call_label_type,
opts.return_label_type, opts.return_label);
ReplaceFst<Arc> rfst(typed_pairs, typed_opts);
// Checks for cyclic dependencies before attempting expansion.
if (rfst.CyclicDependencies()) {
FSTERROR() << "Replace: Cyclic dependencies detected; cannot expand";
ofst->SetProperties(kError, kError);
return;
}
typed_opts.gc = true; // Caching options to speed up batch copy.
typed_opts.gc_limit = 0;
*ofst = rfst;
}
void Replace(const std::vector<LabelFstClassPair> &pairs,
MutableFstClass *ofst, const ReplaceOptions &opts);
} // namespace script
} // namespace fst
#endif // FST_SCRIPT_REPLACE_H_