arcfilter.h revision f4c12fce1ee58e670f9c3fce46c40296ba9ee8a2 
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@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
29namespace fst {
30
31// True for all arcs.
32template <class A>
33class AnyArcFilter {
34public:
35  bool operator()(const A &arc) const { return true; }
36};
37
38
39// True for (input/output) epsilon arcs.
40template <class A>
41class EpsilonArcFilter {
42public:
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.
50template <class A>
51class InputEpsilonArcFilter {
52public:
53  bool operator()(const A &arc) const {
54    return arc.ilabel == 0;
55  }
56};
57
58
59// True for output epsilon arcs.
60template <class A>
61class OutputEpsilonArcFilter {
62public:
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).
71template <class A>
72class MultiLabelArcFilter {
73public:
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
91private:
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