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      1 // arcfilter.h
      2 
      3 // Licensed under the Apache License, Version 2.0 (the "License");
      4 // you may not use this file except in compliance with the License.
      5 // You may obtain a copy of the License at
      6 //
      7 //     http://www.apache.org/licenses/LICENSE-2.0
      8 //
      9 // Unless required by applicable law or agreed to in writing, software
     10 // distributed under the License is distributed on an "AS IS" BASIS,
     11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 // See the License for the specific language governing permissions and
     13 // limitations under the License.
     14 //
     15 // Copyright 2005-2010 Google, Inc.
     16 // Author: riley (at) google.com (Michael Riley)
     17 //
     18 // \file
     19 // Function objects to restrict which arcs are traversed in an FST.
     20 
     21 #ifndef FST_LIB_ARCFILTER_H__
     22 #define FST_LIB_ARCFILTER_H__
     23 
     24 
     25 #include <fst/fst.h>
     26 #include <fst/util.h>
     27 
     28 
     29 namespace fst {
     30 
     31 // True for all arcs.
     32 template <class A>
     33 class AnyArcFilter {
     34 public:
     35   bool operator()(const A &arc) const { return true; }
     36 };
     37 
     38 
     39 // True for (input/output) epsilon arcs.
     40 template <class A>
     41 class EpsilonArcFilter {
     42 public:
     43   bool operator()(const A &arc) const {
     44     return arc.ilabel == 0 && arc.olabel == 0;
     45   }
     46 };
     47 
     48 
     49 // True for input epsilon arcs.
     50 template <class A>
     51 class InputEpsilonArcFilter {
     52 public:
     53   bool operator()(const A &arc) const {
     54     return arc.ilabel == 0;
     55   }
     56 };
     57 
     58 
     59 // True for output epsilon arcs.
     60 template <class A>
     61 class OutputEpsilonArcFilter {
     62 public:
     63   bool operator()(const A &arc) const {
     64     return arc.olabel == 0;
     65   }
     66 };
     67 
     68 
     69 // True if specified labels match (don't match) when keep_match is
     70 // true (false).
     71 template <class A>
     72 class MultiLabelArcFilter {
     73 public:
     74   typedef typename A::Label Label;
     75 
     76   MultiLabelArcFilter(bool match_input = true, bool keep_match = true)
     77     :  match_input_(match_input),
     78        keep_match_(keep_match) {}
     79 
     80 
     81   bool operator()(const A &arc) const {
     82     Label label = match_input_ ? arc.ilabel : arc.olabel;
     83     bool match = labels_.Find(label) != labels_.End();
     84     return keep_match_ ? match : !match;
     85   }
     86 
     87   void AddLabel(Label label) {
     88     labels_.Insert(label);
     89   }
     90 
     91 private:
     92   CompactSet<Label, kNoLabel> labels_;
     93   bool match_input_;
     94   bool keep_match_;
     95 };
     96 
     97 }  // namespace fst
     98 
     99 #endif  // FST_LIB_ARCFILTER_H__
    100