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Diffstat (limited to 'kaldi_io/src/tools/openfst/include/fst/lookahead-filter.h')
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diff --git a/kaldi_io/src/tools/openfst/include/fst/lookahead-filter.h b/kaldi_io/src/tools/openfst/include/fst/lookahead-filter.h new file mode 100644 index 0000000..e11c1bb --- /dev/null +++ b/kaldi_io/src/tools/openfst/include/fst/lookahead-filter.h @@ -0,0 +1,698 @@ +// lookahead-filter.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 +// Composition filters to support lookahead matchers, useful for improving +// composition efficiency with certain inputs. + +#ifndef FST_LIB_LOOKAHEAD_FILTER_H__ +#define FST_LIB_LOOKAHEAD_FILTER_H__ + +#include <vector> +using std::vector; + +#include <fst/fst.h> +#include <fst/lookahead-matcher.h> + + +namespace fst { + +// Identifies and verifies the capabilities of the matcher to be used for +// lookahead with the composition filters below. This version is passed +// the matchers. +template <class M1, class M2> +MatchType LookAheadMatchType(const M1 &m1, const M2 &m2) { + MatchType type1 = m1.Type(false); + MatchType type2 = m2.Type(false); + if (type1 == MATCH_OUTPUT && + m1.Flags() & kOutputLookAheadMatcher) + return MATCH_OUTPUT; + else if (type2 == MATCH_INPUT && + m2.Flags() & kInputLookAheadMatcher) + return MATCH_INPUT; + else if (m1.Flags() & kOutputLookAheadMatcher && + m1.Type(true) == MATCH_OUTPUT) + return MATCH_OUTPUT; + else if (m2.Flags() & kInputLookAheadMatcher && + m2.Type(true) == MATCH_INPUT) + return MATCH_INPUT; + else + return MATCH_NONE; +} + +// Identifies and verifies the capabilities of the matcher to be used for +// lookahead with the composition filters below. This version uses the +// Fst's default matchers. +template <class Arc> +MatchType LookAheadMatchType(const Fst<Arc> &fst1, const Fst<Arc> &fst2) { + LookAheadMatcher< Fst <Arc> > matcher1(fst1, MATCH_OUTPUT); + LookAheadMatcher< Fst <Arc> > matcher2(fst2, MATCH_INPUT); + return LookAheadMatchType(matcher1, matcher2); +} + +// +// LookAheadSelector - a helper class for selecting among possibly +// distinct FST and matcher types w/o using a common base class. This +// lets us avoid virtual function calls. +// + +// Stores and returns the appropriate FST and matcher for lookahead. +// It is templated on the matcher types. General case has no methods +// since not currently supported. +template <class M1, class M2, MatchType MT> +class LookAheadSelector { +}; + +// Stores and returns the appropriate FST and matcher for lookahead. +// Specialized for two matchers of same type with the (match) 'type' +// arg determining which is used for lookahead. +template <class M, MatchType MT> +class LookAheadSelector<M, M, MT> { + public: + typedef typename M::Arc Arc; + typedef typename M::FST F; + + LookAheadSelector(M *lmatcher1, M *lmatcher2, MatchType type) + : lmatcher1_(lmatcher1->Copy()), + lmatcher2_(lmatcher2->Copy()), + type_(type) {} + + LookAheadSelector(const LookAheadSelector<M, M, MT> &selector) + : lmatcher1_(selector.lmatcher1_->Copy()), + lmatcher2_(selector.lmatcher2_->Copy()), + type_(selector.type_) {} + + ~LookAheadSelector() { + delete lmatcher1_; + delete lmatcher2_; + } + + const F &GetFst() const { + return type_ == MATCH_OUTPUT ? lmatcher2_->GetFst() : + lmatcher1_->GetFst(); + } + + M *GetMatcher() const { + return type_ == MATCH_OUTPUT ? lmatcher1_ : lmatcher2_; + } + + private: + M *lmatcher1_; + M *lmatcher2_; + MatchType type_; + + void operator=(const LookAheadSelector<M, M, MT> &); // disallow +}; + +// Stores and returns the appropriate FST and matcher for lookahead. +// Specialized for lookahead on input labels. +template <class M1, class M2> +class LookAheadSelector<M1, M2, MATCH_INPUT> { + public: + typedef typename M1::FST F1; + + LookAheadSelector(M1 *lmatcher1, M2 *lmatcher2, MatchType) + : fst_(lmatcher1->GetFst().Copy()), + lmatcher_(lmatcher2->Copy()) {} + + LookAheadSelector(const LookAheadSelector<M1, M2, MATCH_INPUT> &selector) + : fst_(selector.fst_->Copy()), + lmatcher_(selector.lmatcher_->Copy()) {} + + ~LookAheadSelector() { + delete lmatcher_; + delete fst_; + } + + const F1 &GetFst() const { return *fst_; } + + M2 *GetMatcher() const { return lmatcher_; } + + private: + const F1 *fst_; + M2 *lmatcher_; + + void operator=(const LookAheadSelector<M1, M2, MATCH_INPUT> &); // disallow +}; + + +// Stores and returns the appropriate FST and matcher for lookahead. +// Specialized for lookahead on output labels. +template <class M1, class M2> +class LookAheadSelector<M1, M2, MATCH_OUTPUT> { + public: + typedef typename M2::FST F2; + + LookAheadSelector(M1 *lmatcher1, M2 *lmatcher2, MatchType) + : fst_(lmatcher2->GetFst().Copy()), + lmatcher_(lmatcher1->Copy()) {} + + LookAheadSelector(const LookAheadSelector<M1, M2, MATCH_OUTPUT> &selector) + : fst_(selector.fst_->Copy()), + lmatcher_(selector.lmatcher_->Copy()) {} + + ~LookAheadSelector() { + delete lmatcher_; + delete fst_; + } + + const F2 &GetFst() const { return *fst_; } + + M1 *GetMatcher() const { return lmatcher_; } + + private: + const F2 *fst_; + M1 *lmatcher_; + + void operator=(const LookAheadSelector<M1, M2, MATCH_OUTPUT> &); // disallow +}; + +// This filter uses a lookahead matcher in FilterArc(arc1, arc2) to +// examine the future of the composition state (arc1.nextstate, +// arc2.nextstate), blocking moving forward when its determined to be +// non-coaccessible. It is templated on an underlying filter, +// typically the epsilon filter. Which matcher is the lookahead +// matcher is determined by the template argument MT unless it is +// MATCH_BOTH. In that case, both matcher arguments must be lookahead +// matchers of the same type and one will be selected by +// LookAheadMatchType() based on their capability. +template <class F, + class M1 = LookAheadMatcher<typename F::FST1>, + class M2 = M1, + MatchType MT = MATCH_BOTH> +class LookAheadComposeFilter { + public: + typedef typename F::FST1 FST1; + typedef typename F::FST2 FST2; + typedef typename F::Arc Arc; + typedef typename F::Matcher1 Matcher1; + typedef typename F::Matcher2 Matcher2; + typedef typename F::FilterState FilterState; + typedef LookAheadComposeFilter<F, M1, M2, MT> Filter; + + typedef typename Arc::StateId StateId; + typedef typename Arc::Label Label; + typedef typename Arc::Weight Weight; + + LookAheadComposeFilter(const FST1 &fst1, const FST2 &fst2, + M1 *matcher1, M2 *matcher2) + : filter_(fst1, fst2, matcher1, matcher2), + lookahead_type_(MT == MATCH_BOTH ? + LookAheadMatchType(*filter_.GetMatcher1(), + *filter_.GetMatcher2()) : MT), + selector_(filter_.GetMatcher1(), filter_.GetMatcher2(), + lookahead_type_), + flags_(lookahead_type_ == MATCH_OUTPUT ? + filter_.GetMatcher1()->Flags() : + filter_.GetMatcher2()->Flags()) { + if (lookahead_type_ == MATCH_NONE) { + FSTERROR() << "LookAheadComposeFilter: 1st argument cannot " + << "match/look-ahead on output labels and 2nd argument " + << "cannot match/look-ahead on input labels."; + } + selector_.GetMatcher()->InitLookAheadFst(selector_.GetFst()); + } + + LookAheadComposeFilter(const LookAheadComposeFilter<F, M1, M2, MT> &filter, + bool safe = false) + : filter_(filter.filter_, safe), + lookahead_type_(filter.lookahead_type_), + selector_(filter_.GetMatcher1(), filter_.GetMatcher2(), + lookahead_type_), + flags_(filter.flags_) { + selector_.GetMatcher()->InitLookAheadFst(selector_.GetFst(), true); + } + + FilterState Start() const { + return filter_.Start(); + } + + void SetState(StateId s1, StateId s2, const FilterState &f) { + filter_.SetState(s1, s2, f); + } + + FilterState FilterArc(Arc *arc1, Arc *arc2) const { + lookahead_arc_ = false; + + const FilterState &f = filter_.FilterArc(arc1, arc2); + if (f == FilterState::NoState()) + return FilterState::NoState(); + + return LookAheadOutput() ? LookAheadFilterArc(arc1, arc2, f) : + LookAheadFilterArc(arc2, arc1, f); + } + + void FilterFinal(Weight *weight1, Weight *weight2) const { + filter_.FilterFinal(weight1, weight2); + } + + // Return resp matchers. Ownership stays with filter. + Matcher1 *GetMatcher1() { return filter_.GetMatcher1(); } + Matcher2 *GetMatcher2() { return filter_.GetMatcher2(); } + + const LookAheadSelector<Matcher1, Matcher2, MT> &Selector() const { + return selector_; + } + + uint64 Properties(uint64 inprops) const { + uint64 outprops = filter_.Properties(inprops); + if (lookahead_type_ == MATCH_NONE) + outprops |= kError; + return outprops; + } + + uint32 LookAheadFlags() const { return flags_; } + + bool LookAheadArc() const { return lookahead_arc_; } + + bool LookAheadOutput() const { + if (MT == MATCH_OUTPUT) + return true; + else if (MT == MATCH_INPUT) + return false; + else if (lookahead_type_ == MATCH_OUTPUT) + return true; + else + return false; + } + + private: + FilterState LookAheadFilterArc(Arc *arca, Arc *arcb, + const FilterState &f) const { + Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel; + + if (labela != 0 && !(flags_ & kLookAheadNonEpsilons)) + return f; + if (labela == 0 && !(flags_ & kLookAheadEpsilons)) + return f; + + lookahead_arc_ = true; + selector_.GetMatcher()->SetState(arca->nextstate); + + return selector_.GetMatcher()->LookAheadFst(selector_.GetFst(), + arcb->nextstate) ? f : + FilterState::NoState(); + } + + F filter_; // Underlying filter + MatchType lookahead_type_; // Lookahead match type + LookAheadSelector<Matcher1, Matcher2, MT> selector_; + uint32 flags_; // Lookahead flags + mutable bool lookahead_arc_; // Look-ahead performed at last FilterArc()? + + void operator=(const LookAheadComposeFilter<F, M1, M2> &); // disallow +}; + + +// This filter adds weight-pushing to a lookahead composition filter +// using the LookAheadWeight() method of matcher argument. It is +// templated on an underlying lookahead filter, typically the basic +// lookahead filter. Weight-pushing in composition brings weights +// forward as much as possible based on the lookahead information. +template <class F, + class M1 = LookAheadMatcher<typename F::FST1>, + class M2 = M1, + MatchType MT = MATCH_BOTH> +class PushWeightsComposeFilter { + public: + typedef typename F::FST1 FST1; + typedef typename F::FST2 FST2; + typedef typename F::Arc Arc; + typedef typename F::Matcher1 Matcher1; + typedef typename F::Matcher2 Matcher2; + typedef typename F::FilterState FilterState1; + typedef WeightFilterState<typename Arc::Weight> FilterState2; + typedef PairFilterState<FilterState1, FilterState2> FilterState; + + typedef typename Arc::StateId StateId; + typedef typename Arc::Label Label; + typedef typename Arc::Weight Weight; + + PushWeightsComposeFilter(const FST1 &fst1, const FST2 &fst2, + M1 *matcher1, M2 *matcher2) + : filter_(fst1, fst2, matcher1, matcher2), + f_(FilterState::NoState()) {} + + PushWeightsComposeFilter(const PushWeightsComposeFilter<F, M1, M2, MT> + &filter, + bool safe = false) + : filter_(filter.filter_, safe), + f_(FilterState::NoState()) {} + + FilterState Start() const { + return FilterState(filter_.Start(), FilterState2(Weight::One())); + } + + void SetState(StateId s1, StateId s2, const FilterState &f) { + f_ = f; + filter_.SetState(s1, s2, f.GetState1()); + } + + FilterState FilterArc(Arc *arc1, Arc *arc2) const { + const FilterState1 &f1 = filter_.FilterArc(arc1, arc2); + if (f1 == FilterState1::NoState()) + return FilterState::NoState(); + + if (!(LookAheadFlags() & kLookAheadWeight)) + return FilterState(f1, FilterState2(Weight::One())); + + const Weight &lweight = filter_.LookAheadArc() ? + Selector().GetMatcher()->LookAheadWeight() : Weight::One(); + const FilterState2 &f2 = f_.GetState2(); + const Weight &fweight = f2.GetWeight(); + + arc2->weight = Divide(Times(arc2->weight, lweight), fweight); + return FilterState(f1, FilterState2(lweight)); + } + + void FilterFinal(Weight *weight1, Weight *weight2) const { + filter_.FilterFinal(weight1, weight2); + if (!(LookAheadFlags() & kLookAheadWeight) || *weight1 == Weight::Zero()) + return; + + const FilterState2 &f2 = f_.GetState2(); + const Weight &fweight = f2.GetWeight(); + *weight1 = Divide(*weight1, fweight); + } + // Return resp matchers. Ownership states with filter. + Matcher1 *GetMatcher1() { return filter_.GetMatcher1(); } + Matcher2 *GetMatcher2() { return filter_.GetMatcher2(); } + + const LookAheadSelector<Matcher1, Matcher2, MT> &Selector() const { + return filter_.Selector(); + } + + uint32 LookAheadFlags() const { return filter_.LookAheadFlags(); } + bool LookAheadArc() const { return filter_.LookAheadArc(); } + bool LookAheadOutput() const { return filter_.LookAheadOutput(); } + + uint64 Properties(uint64 props) const { + return filter_.Properties(props) & kWeightInvariantProperties; + } + + private: + F filter_; // Underlying filter + FilterState f_; // Current filter state + + void operator=(const PushWeightsComposeFilter<F, M1, M2, MT> &); // disallow +}; + +// This filter adds label-pushing to a lookahead composition filter +// using the LookAheadPrefix() method of the matcher argument. It is +// templated on an underlying filter, typically the basic lookahead +// or weight-pushing lookahead filter. Label-pushing in composition +// matches labels as early as possible based on the lookahead +// information. +template <class F, + class M1 = LookAheadMatcher<typename F::FST1>, + class M2 = M1, + MatchType MT = MATCH_BOTH> +class PushLabelsComposeFilter { + public: + typedef typename F::FST1 FST1; + typedef typename F::FST2 FST2; + typedef typename F::Arc Arc; + typedef typename Arc::StateId StateId; + typedef typename Arc::Label Label; + typedef typename Arc::Weight Weight; + + typedef MultiEpsMatcher<typename F::Matcher1> Matcher1; + typedef MultiEpsMatcher<typename F::Matcher2> Matcher2; + typedef typename F::FilterState FilterState1; + typedef IntegerFilterState<typename Arc::Label> FilterState2; + typedef PairFilterState<FilterState1, FilterState2> FilterState; + + PushLabelsComposeFilter(const FST1 &fst1, const FST2 &fst2, + M1 *matcher1, M2 *matcher2) + : filter_(fst1, fst2, matcher1, matcher2), + f_(FilterState::NoState()), + fst1_(filter_.GetMatcher1()->GetFst()), + fst2_(filter_.GetMatcher2()->GetFst()), + matcher1_(fst1_, MATCH_OUTPUT, + filter_.LookAheadOutput() ? kMultiEpsList : kMultiEpsLoop, + filter_.GetMatcher1(), + false), + matcher2_(fst2_, MATCH_INPUT, + filter_.LookAheadOutput() ? kMultiEpsLoop : kMultiEpsList, + filter_.GetMatcher2(), + false) {} + + PushLabelsComposeFilter(const PushLabelsComposeFilter<F, M1, M2, MT> &filter, + bool safe = false) + : filter_(filter.filter_, safe), + f_(FilterState::NoState()), + fst1_(filter_.GetMatcher1()->GetFst()), + fst2_(filter_.GetMatcher2()->GetFst()), + matcher1_(fst1_, MATCH_OUTPUT, + filter_.LookAheadOutput() ? kMultiEpsList : kMultiEpsLoop, + filter_.GetMatcher1(), + false), + matcher2_(fst2_, MATCH_INPUT, + filter_.LookAheadOutput() ? kMultiEpsLoop : kMultiEpsList, + filter_.GetMatcher2(), + false) { + } + + FilterState Start() const { + return FilterState(filter_.Start(), FilterState2(kNoLabel)); + } + + void SetState(StateId s1, StateId s2, const FilterState &f) { + f_ = f; + filter_.SetState(s1, s2, f.GetState1()); + if (!(LookAheadFlags() & kLookAheadPrefix)) + return; + + narcsa_ = LookAheadOutput() ? internal::NumArcs(fst1_, s1) + : internal::NumArcs(fst2_, s2); + + const FilterState2 &f2 = f_.GetState2(); + const Label &flabel = f2.GetState(); + + GetMatcher1()->ClearMultiEpsLabels(); + GetMatcher2()->ClearMultiEpsLabels(); + if (flabel != kNoLabel) { // Have a lookahead label? + GetMatcher1()->AddMultiEpsLabel(flabel); // Yes, make it a multi-epsilon + GetMatcher2()->AddMultiEpsLabel(flabel); // label so that it matches the + } // implicit epsilon arc to be + } // modified below when pushing. + + FilterState FilterArc(Arc *arc1, Arc *arc2) const { + if (!(LookAheadFlags() & kLookAheadPrefix)) + return FilterState(filter_.FilterArc(arc1, arc2), + FilterState2(kNoLabel)); + + const FilterState2 &f2 = f_.GetState2(); + const Label &flabel = f2.GetState(); + if (flabel != kNoLabel) // Have a lookahead label? + return LookAheadOutput() ? PushedLabelFilterArc(arc1, arc2, flabel) : + PushedLabelFilterArc(arc2, arc1, flabel); + + const FilterState1 &f1 = filter_.FilterArc(arc1, arc2); + if (f1 == FilterState1::NoState()) + return FilterState::NoState(); + + if (!filter_.LookAheadArc()) + return FilterState(f1, FilterState2(kNoLabel)); + + return LookAheadOutput() ? PushLabelFilterArc(arc1, arc2, f1) : + PushLabelFilterArc(arc2, arc1, f1); + } + + void FilterFinal(Weight *weight1, Weight *weight2) const { + filter_.FilterFinal(weight1, weight2); + if (!(LookAheadFlags() & kLookAheadPrefix) || + *weight1 == Weight::Zero()) + return; + + const FilterState2 &f2 = f_.GetState2(); + const Label &flabel = f2.GetState(); + if (flabel != kNoLabel) + *weight1 = Weight::Zero(); + } + + // Return resp matchers. Ownership states with filter. + Matcher1 *GetMatcher1() { return &matcher1_; } + Matcher2 *GetMatcher2() { return &matcher2_; } + + uint64 Properties(uint64 iprops) const { + uint64 oprops = filter_.Properties(iprops); + if (LookAheadOutput()) + return oprops & kOLabelInvariantProperties; + else + return oprops & kILabelInvariantProperties; + } + + private: + const LookAheadSelector<typename F::Matcher1, typename F::Matcher2, MT> + &Selector() const { + return filter_.Selector(); + } + + // Consumes an already pushed label. + FilterState PushedLabelFilterArc(Arc *arca, Arc *arcb, + Label flabel) const { + Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel; + const Label &labelb = LookAheadOutput() ? arcb->ilabel : arcb->olabel; + + if (labelb != kNoLabel) { + return FilterState::NoState(); // Block non- (multi-) epsilon label + } else if (labela == flabel) { + labela = 0; // Convert match to multi-eps to eps + return Start(); + } else if (labela == 0) { + if (narcsa_ == 1) + return f_; // Take eps; keep state w/ label + Selector().GetMatcher()->SetState(arca->nextstate); + if (Selector().GetMatcher()->LookAheadLabel(flabel)) + return f_; // Take eps; keep state w/ label + else + return FilterState::NoState(); // Block non-coaccessible path + } else { + return FilterState::NoState(); // Block mismatch to multi-eps label + } + } + + // Pushes a label forward when possible. + FilterState PushLabelFilterArc(Arc *arca, Arc *arcb, + const FilterState1 &f1) const { + Label &labela = LookAheadOutput() ? arca->olabel : arca->ilabel; + const Label &labelb = LookAheadOutput() ? arcb->olabel : arcb->ilabel; + + if (labelb != 0) // No place to push. + return FilterState(f1, FilterState2(kNoLabel)); + if (labela != 0 && // Wrong lookahead prefix type? + LookAheadFlags() & kLookAheadNonEpsilonPrefix) + return FilterState(f1, FilterState2(kNoLabel)); + + Arc larc(kNoLabel, kNoLabel, Weight::Zero(), kNoStateId); + + if (Selector().GetMatcher()->LookAheadPrefix(&larc)) { // Have prefix arc? + labela = LookAheadOutput() ? larc.ilabel : larc.olabel; + arcb->ilabel = larc.ilabel; // Yes, go forward on that arc, + arcb->olabel = larc.olabel; // thus pushing the label. + arcb->weight = Times(arcb->weight, larc.weight); + arcb->nextstate = larc.nextstate; + return FilterState(f1, FilterState2(labela)); + } else { + return FilterState(f1, FilterState2(kNoLabel)); + } + } + + uint32 LookAheadFlags() const { return filter_.LookAheadFlags(); } + bool LookAheadArc() const { return filter_.LookAheadArc(); } + bool LookAheadOutput() const { return filter_.LookAheadOutput(); } + + F filter_; // Underlying filter + FilterState f_ ; // Current filter state + const FST1 &fst1_; + const FST2 &fst2_; + Matcher1 matcher1_; // Multi-epsilon matcher for fst1 + Matcher2 matcher2_; // Multi-epsilon matcher for fst2 + ssize_t narcsa_; // Number of arcs leaving look-ahead match FST + + void operator=(const PushLabelsComposeFilter<F, M1, M2, MT> &); // disallow +}; + +// +// CONVENIENCE CLASS useful for setting up composition with a default +// look-ahead matcher and filter. +// + +template <class A, MatchType type> // MATCH_NONE +class DefaultLookAhead { + public: + typedef Matcher< Fst<A> > M; + typedef SequenceComposeFilter<M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for MATCH_INPUT to allow lookahead. +template <class A> +class DefaultLookAhead<A, MATCH_INPUT> { + public: + typedef LookAheadMatcher< Fst<A> > M; + typedef SequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for MATCH_OUTPUT to allow lookahead. +template <class A> +class DefaultLookAhead<A, MATCH_OUTPUT> { + public: + typedef LookAheadMatcher< Fst<A> > M; + typedef AltSequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for StdArc to allow weight and label pushing. +template <> +class DefaultLookAhead<StdArc, MATCH_INPUT> { + public: + typedef StdArc A; + typedef LookAheadMatcher< Fst<A> > M; + typedef SequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> LF; + typedef PushWeightsComposeFilter<LF, M> WF; + typedef PushLabelsComposeFilter<WF, M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for StdArc to allow weight and label pushing. +template <> +class DefaultLookAhead<StdArc, MATCH_OUTPUT> { + public: + typedef StdArc A; + typedef LookAheadMatcher< Fst<A> > M; + typedef AltSequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> LF; + typedef PushWeightsComposeFilter<LF, M> WF; + typedef PushLabelsComposeFilter<WF, M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for LogArc to allow weight and label pushing. +template <> +class DefaultLookAhead<LogArc, MATCH_INPUT> { + public: + typedef LogArc A; + typedef LookAheadMatcher< Fst<A> > M; + typedef SequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> LF; + typedef PushWeightsComposeFilter<LF, M> WF; + typedef PushLabelsComposeFilter<WF, M> ComposeFilter; + typedef M FstMatcher; +}; + +// Specializes for LogArc to allow weight and label pushing. +template <> +class DefaultLookAhead<LogArc, MATCH_OUTPUT> { + public: + typedef LogArc A; + typedef LookAheadMatcher< Fst<A> > M; + typedef AltSequenceComposeFilter<M> SF; + typedef LookAheadComposeFilter<SF, M> LF; + typedef PushWeightsComposeFilter<LF, M> WF; + typedef PushLabelsComposeFilter<WF, M> ComposeFilter; + typedef M FstMatcher; +}; + +} // namespace fst + +#endif // FST_LIB_LOOKAHEAD_FILTER_H__ |