antlr.v4.runtime.atn.Transition source code

1 /*
2  * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
3  * Use of this file is governed by the BSD 3-clause license that
4  * can be found in the LICENSE.txt file in the project root.
5  */
6 
7 module antlr.v4.runtime.atn.Transition;
8 
9 import std.conv;
10 import antlr.v4.runtime.atn.TransitionStates;
11 import antlr.v4.runtime.atn.EpsilonTransition;
12 import antlr.v4.runtime.atn.RuleTransition;
13 import antlr.v4.runtime.atn.PredicateTransition;
14 import antlr.v4.runtime.atn.RangeTransition;
15 import antlr.v4.runtime.atn.AtomTransition;
16 import antlr.v4.runtime.atn.ActionTransition;
17 import antlr.v4.runtime.atn.SetTransition;
18 import antlr.v4.runtime.atn.NotSetTransition;
19 import antlr.v4.runtime.atn.WildcardTransition;
20 import antlr.v4.runtime.atn.PrecedencePredicateTransition;
21 import antlr.v4.runtime.atn.ATNState;
22 import antlr.v4.runtime.misc.IntervalSet;
23 
24 /**
25  * An ATN transition between any two ATN states.  Subclasses define
26  * atom, set, epsilon, action, predicate, rule transitions.
27  *
28  * <p>This is a one way link.  It emanates from a state (usually via a list of
29  * transitions) and has a target state.</p>
30  *
31  * <p>Since we never have to change the ATN transitions once we construct it,
32  * we can fix these transitions as specific classes. The DFA transitions
33  * on the other hand need to update the labels as it adds transitions to
34  * the states. We'll use the term Edge for the DFA to distinguish them from
35  * ATN transitions.</p>
36  */
37 abstract class Transition
38 {
39 
40     /**
41      * The target of this transition.
42      */
43     public ATNState target;
44 
45     public static string[] serializationNames = [
46         "INVALID",
47         "EPSILON",
48         "RANGE",
49         "RULE",
50         "PREDICATE",
51         "ATOM",
52         "ACTION",
53         "SET",
54         "NOT_SET",
55         "WILDCARD",
56         "PRECEDENCE"
57     ];
58 
59     public this(ATNState target)
60     {
61         this.target = target;
62     }
63 
64     public this()
65     {
66     }
67 
68     abstract public int getSerializationType();
69 
70     /**
71      * Determines if the transition is an "epsilon" transition.
72      *
73      * <p>The default implementation returns {@code false}.</p>
74      *
75      *  @return {@code true} if traversing this transition in the ATN does not
76      *  consume an input symbol; otherwise, {@code false} if traversing this
77      *  transition consumes (matches) an input symbol.
78      */
79     public bool isEpsilon()
80     {
81         return false;
82     }
83 
84     public IntervalSet label()
85     {
86         return null;
87     }
88 
89     abstract public bool matches(int symbol, int minVocabSymbol, int maxVocabSymbol);
90 
91 }