/usr/include/fst/extensions/mpdt/expand.h is in libfst-dev 1.6.3-2.
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// finite-state transducer library.
//
// Expands an MPDT to an FST.
#ifndef FST_EXTENSIONS_MPDT_EXPAND_H_
#define FST_EXTENSIONS_MPDT_EXPAND_H_
#include <vector>
#include <fst/extensions/mpdt/mpdt.h>
#include <fst/extensions/pdt/paren.h>
#include <fst/cache.h>
#include <fst/mutable-fst.h>
#include <fst/queue.h>
#include <fst/state-table.h>
#include <fst/test-properties.h>
namespace fst {
template <class Arc>
struct MPdtExpandFstOptions : public CacheOptions {
bool keep_parentheses;
internal::MPdtStack<typename Arc::StateId, typename Arc::Label> *stack;
PdtStateTable<typename Arc::StateId, typename Arc::StateId> *state_table;
MPdtExpandFstOptions(
const CacheOptions &opts = CacheOptions(), bool kp = false,
internal::MPdtStack<typename Arc::StateId, typename Arc::Label> *s =
nullptr,
PdtStateTable<typename Arc::StateId, typename Arc::StateId> *st = nullptr)
: CacheOptions(opts), keep_parentheses(kp), stack(s), state_table(st) {}
};
// Properties for an expanded PDT.
inline uint64 MPdtExpandProperties(uint64 inprops) {
return inprops & (kAcceptor | kAcyclic | kInitialAcyclic | kUnweighted);
}
namespace internal {
// Implementation class for ExpandFst
template <class Arc>
class MPdtExpandFstImpl : public CacheImpl<Arc> {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
using StackId = StateId;
using StateTuple = PdtStateTuple<StateId, StackId>;
using ParenStack = internal::MPdtStack<StateId, Label>;
using FstImpl<Arc>::SetType;
using FstImpl<Arc>::SetProperties;
using FstImpl<Arc>::Properties;
using FstImpl<Arc>::SetInputSymbols;
using FstImpl<Arc>::SetOutputSymbols;
using CacheBaseImpl<CacheState<Arc>>::PushArc;
using CacheBaseImpl<CacheState<Arc>>::HasArcs;
using CacheBaseImpl<CacheState<Arc>>::HasFinal;
using CacheBaseImpl<CacheState<Arc>>::HasStart;
using CacheBaseImpl<CacheState<Arc>>::SetArcs;
using CacheBaseImpl<CacheState<Arc>>::SetFinal;
using CacheBaseImpl<CacheState<Arc>>::SetStart;
MPdtExpandFstImpl(const Fst<Arc> &fst,
const std::vector<std::pair<Label, Label>> &parens,
const std::vector<Label> &assignments,
const MPdtExpandFstOptions<Arc> &opts)
: CacheImpl<Arc>(opts),
fst_(fst.Copy()),
stack_(opts.stack ? opts.stack : new ParenStack(parens, assignments)),
state_table_(opts.state_table ? opts.state_table
: new PdtStateTable<StateId, StackId>()),
own_stack_(!opts.stack),
own_state_table_(!opts.state_table),
keep_parentheses_(opts.keep_parentheses) {
SetType("expand");
const auto props = fst.Properties(kFstProperties, false);
SetProperties(MPdtExpandProperties(props), kCopyProperties);
SetInputSymbols(fst.InputSymbols());
SetOutputSymbols(fst.OutputSymbols());
}
MPdtExpandFstImpl(const MPdtExpandFstImpl &impl)
: CacheImpl<Arc>(impl),
fst_(impl.fst_->Copy(true)),
stack_(new ParenStack(*impl.stack_)),
state_table_(new PdtStateTable<StateId, StackId>()),
own_stack_(true),
own_state_table_(true),
keep_parentheses_(impl.keep_parentheses_) {
SetType("expand");
SetProperties(impl.Properties(), kCopyProperties);
SetInputSymbols(impl.InputSymbols());
SetOutputSymbols(impl.OutputSymbols());
}
~MPdtExpandFstImpl() override {
if (own_stack_) delete stack_;
if (own_state_table_) delete state_table_;
}
StateId Start() {
if (!HasStart()) {
const auto s = fst_->Start();
if (s == kNoStateId) return kNoStateId;
const StateTuple tuple(s, 0);
const auto start = state_table_->FindState(tuple);
SetStart(start);
}
return CacheImpl<Arc>::Start();
}
Weight Final(StateId s) {
if (!HasFinal(s)) {
const auto &tuple = state_table_->Tuple(s);
const auto weight = fst_->Final(tuple.state_id);
SetFinal(s,
(weight != Weight::Zero() && tuple.stack_id == 0)
? weight
: Weight::Zero());
}
return CacheImpl<Arc>::Final(s);
}
size_t NumArcs(StateId s) {
if (!HasArcs(s)) ExpandState(s);
return CacheImpl<Arc>::NumArcs(s);
}
size_t NumInputEpsilons(StateId s) {
if (!HasArcs(s)) ExpandState(s);
return CacheImpl<Arc>::NumInputEpsilons(s);
}
size_t NumOutputEpsilons(StateId s) {
if (!HasArcs(s)) ExpandState(s);
return CacheImpl<Arc>::NumOutputEpsilons(s);
}
void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) {
if (!HasArcs(s)) ExpandState(s);
CacheImpl<Arc>::InitArcIterator(s, data);
}
// Computes the outgoing transitions from a state, creating new destination
// states as needed.
void ExpandState(StateId s) {
const auto tuple = state_table_->Tuple(s);
for (ArcIterator<Fst<Arc>> aiter(*fst_, tuple.state_id); !aiter.Done();
aiter.Next()) {
auto arc = aiter.Value();
const auto stack_id = stack_->Find(tuple.stack_id, arc.ilabel);
if (stack_id == -1) {
continue; // Non-matching close parenthesis.
} else if ((stack_id != tuple.stack_id) && !keep_parentheses_) {
arc.ilabel = arc.olabel = 0; // Stack push/pop.
}
const StateTuple ntuple(arc.nextstate, stack_id);
arc.nextstate = state_table_->FindState(ntuple);
PushArc(s, arc);
}
SetArcs(s);
}
const ParenStack &GetStack() const { return *stack_; }
const PdtStateTable<StateId, StackId> &GetStateTable() const {
return *state_table_;
}
private:
std::unique_ptr<const Fst<Arc>> fst_;
ParenStack *stack_;
PdtStateTable<StateId, StackId> *state_table_;
const bool own_stack_;
const bool own_state_table_;
const bool keep_parentheses_;
MPdtExpandFstImpl &operator=(const MPdtExpandFstImpl &) = delete;
};
} // namespace internal
// Expands a multi-pushdown transducer (MPDT) encoded as an FST into an FST.
// This version is a delayed FST. In the MPDT, some transitions are labeled with
// open or close parentheses. To be interpreted as an MPDT, the parens for each
// stack must balance on a path. The open-close parenthesis label
// pairs are passed using the parens argument, and the assignment of those pairs
// to stacks is passed using the assignments argument. Expansion enforces the
// parenthesis constraints. The MPDT must be
// expandable as an FST.
//
// This class attaches interface to implementation and handles
// reference counting, delegating most methods to ImplToFst.
template <class A>
class MPdtExpandFst : public ImplToFst<internal::MPdtExpandFstImpl<A>> {
public:
using Arc = A;
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
using StackId = StateId;
using ParenStack = internal::MPdtStack<StackId, Label>;
using Store = DefaultCacheStore<Arc>;
using State = typename Store::State;
using Impl = internal::MPdtExpandFstImpl<Arc>;
friend class ArcIterator<MPdtExpandFst<Arc>>;
friend class StateIterator<MPdtExpandFst<Arc>>;
MPdtExpandFst(const Fst<Arc> &fst,
const std::vector<std::pair<Label, Label>> &parens,
const std::vector<Label> &assignments)
: ImplToFst<Impl>(std::make_shared<Impl>(fst, parens, assignments,
MPdtExpandFstOptions<Arc>())) {}
MPdtExpandFst(const Fst<Arc> &fst,
const std::vector<std::pair<Label, Label>> &parens,
const std::vector<Label> &assignments,
const MPdtExpandFstOptions<Arc> &opts)
: ImplToFst<Impl>(
std::make_shared<Impl>(fst, parens, assignments, opts)) {}
// See Fst<>::Copy() for doc.
MPdtExpandFst(const MPdtExpandFst<Arc> &fst, bool safe = false)
: ImplToFst<Impl>(fst, safe) {}
// Get a copy of this ExpandFst. See Fst<>::Copy() for further doc.
MPdtExpandFst<Arc> *Copy(bool safe = false) const override {
return new MPdtExpandFst<A>(*this, safe);
}
inline void InitStateIterator(StateIteratorData<Arc> *data) const override;
void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const override {
GetMutableImpl()->InitArcIterator(s, data);
}
const ParenStack &GetStack() const { return GetImpl()->GetStack(); }
const PdtStateTable<StateId, StackId> &GetStateTable() const {
return GetImpl()->GetStateTable();
}
private:
using ImplToFst<Impl>::GetImpl;
using ImplToFst<Impl>::GetMutableImpl;
void operator=(const MPdtExpandFst &) = delete;
};
// Specialization for MPdtExpandFst.
template <class Arc>
class StateIterator<MPdtExpandFst<Arc>>
: public CacheStateIterator<MPdtExpandFst<Arc>> {
public:
explicit StateIterator(const MPdtExpandFst<Arc> &fst)
: CacheStateIterator<MPdtExpandFst<Arc>>(fst, fst.GetMutableImpl()) {}
};
// Specialization for MPdtExpandFst.
template <class Arc>
class ArcIterator<MPdtExpandFst<Arc>>
: public CacheArcIterator<MPdtExpandFst<Arc>> {
public:
using StateId = typename Arc::StateId;
ArcIterator(const MPdtExpandFst<Arc> &fst, StateId s)
: CacheArcIterator<MPdtExpandFst<Arc>>(fst.GetMutableImpl(), s) {
if (!fst.GetImpl()->HasArcs(s)) fst.GetMutableImpl()->ExpandState(s);
}
};
template <class Arc>
inline void MPdtExpandFst<Arc>::InitStateIterator(
StateIteratorData<Arc> *data) const {
data->base = new StateIterator<MPdtExpandFst<Arc>>(*this);
}
struct MPdtExpandOptions {
bool connect;
bool keep_parentheses;
explicit MPdtExpandOptions(bool connect = true, bool keep_parentheses = false)
: connect(connect), keep_parentheses(keep_parentheses) {}
};
// Expands a multi-pushdown transducer (MPDT) encoded as an FST into an FST.
// This version writes the expanded PDT to a mutable FST. In the MPDT, some
// transitions are labeled with open or close parentheses. To be interpreted as
// an MPDT, the parens for each stack must balance on a path. The open-close
// parenthesis label pair sets are passed using the parens argument, and the
// assignment of those pairs to stacks is passed using the assignments argument.
// The expansion enforces the parenthesis constraints. The MPDT must be
// expandable as an FST.
template <class Arc>
void Expand(const Fst<Arc> &ifst,
const std::vector<
std::pair<typename Arc::Label, typename Arc::Label>> &parens,
const std::vector<typename Arc::Label> &assignments,
MutableFst<Arc> *ofst, const MPdtExpandOptions &opts) {
MPdtExpandFstOptions<Arc> eopts;
eopts.gc_limit = 0;
eopts.keep_parentheses = opts.keep_parentheses;
*ofst = MPdtExpandFst<Arc>(ifst, parens, assignments, eopts);
if (opts.connect) Connect(ofst);
}
// Expands a multi-pushdown transducer (MPDT) encoded as an FST into an FST.
// This version writes the expanded PDT to a mutable FST. In the MPDT, some
// transitions are labeled with open or close parentheses. To be interpreted as
// an MPDT, the parens for each stack must balance on a path. The open-close
// parenthesis label pair sets are passed using the parens argument, and the
// assignment of those pairs to stacks is passed using the assignments argument.
// The expansion enforces the parenthesis constraints. The MPDT must be
// expandable as an FST.
template <class Arc>
void Expand(const Fst<Arc> &ifst,
const std::vector<std::pair<typename Arc::Label,
typename Arc::Label>> &parens,
const std::vector<typename Arc::Label> &assignments,
MutableFst<Arc> *ofst, bool connect = true,
bool keep_parentheses = false) {
const MPdtExpandOptions opts(connect, keep_parentheses);
Expand(ifst, parens, assignments, ofst, opts);
}
} // namespace fst
#endif // FST_EXTENSIONS_MPDT_EXPAND_H_
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