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/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.runtime.atn;

import org.antlr.v4.runtime.misc.IntervalSet;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/** An ATN transition between any two ATN states.  Subclasses define
 *  atom, set, epsilon, action, predicate, rule transitions.
 *
 *  

This is a one way link. It emanates from a state (usually via a list of * transitions) and has a target state.

* *

Since we never have to change the ATN transitions once we construct it, * we can fix these transitions as specific classes. The DFA transitions * on the other hand need to update the labels as it adds transitions to * the states. We'll use the term Edge for the DFA to distinguish them from * ATN transitions.

*/ public abstract class Transition { // constants for serialization public static final int EPSILON = 1; public static final int RANGE = 2; public static final int RULE = 3; public static final int PREDICATE = 4; // e.g., {isType(input.LT(1))}? public static final int ATOM = 5; public static final int ACTION = 6; public static final int SET = 7; // ~(A|B) or ~atom, wildcard, which convert to next 2 public static final int NOT_SET = 8; public static final int WILDCARD = 9; public static final int PRECEDENCE = 10; public static final List serializationNames = Collections.unmodifiableList(Arrays.asList( "INVALID", "EPSILON", "RANGE", "RULE", "PREDICATE", "ATOM", "ACTION", "SET", "NOT_SET", "WILDCARD", "PRECEDENCE" )); public static final Map, Integer> serializationTypes = Collections.unmodifiableMap(new HashMap, Integer>() {{ put(EpsilonTransition.class, EPSILON); put(RangeTransition.class, RANGE); put(RuleTransition.class, RULE); put(PredicateTransition.class, PREDICATE); put(AtomTransition.class, ATOM); put(ActionTransition.class, ACTION); put(SetTransition.class, SET); put(NotSetTransition.class, NOT_SET); put(WildcardTransition.class, WILDCARD); put(PrecedencePredicateTransition.class, PRECEDENCE); }}); /** The target of this transition. */ public ATNState target; protected Transition(ATNState target) { if (target == null) { throw new NullPointerException("target cannot be null."); } this.target = target; } public abstract int getSerializationType(); /** * Determines if the transition is an "epsilon" transition. * *

The default implementation returns {@code false}.

* * @return {@code true} if traversing this transition in the ATN does not * consume an input symbol; otherwise, {@code false} if traversing this * transition consumes (matches) an input symbol. */ public boolean isEpsilon() { return false; } public IntervalSet label() { return null; } public abstract boolean matches(int symbol, int minVocabSymbol, int maxVocabSymbol); }




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