xref: /external/antlr/antlr-3.4/tool/src/main/java/org/antlr/analysis/Transition.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */
package org.antlr.analysis;

/** A generic transition between any two state machine states.  It defines
 *  some special labels that indicate things like epsilon transitions and
 *  that the label is actually a set of labels or a semantic predicate.
 *  This is a one way link.  It emanates from a state (usually via a list of
 *  transitions) and has a label/target pair.  I have abstracted the notion
 *  of a Label to handle the various kinds of things it can be.
 */
public class Transition implements Comparable {
    /** What label must be consumed to transition to target */
    public Label label;

    /** The target of this transition */
    public State target;

    public Transition(Label label, State target) {
        this.label = label;
        this.target = target;
    }

    public Transition(int label, State target) {
        this.label = new Label(label);
        this.target = target;
    }

	public boolean isEpsilon() {
		return label.isEpsilon();
	}

	public boolean isAction() {
		return label.isAction();
	}

    public boolean isSemanticPredicate() {
        return label.isSemanticPredicate();
    }

    public int hashCode() {
        return label.hashCode() + target.stateNumber;
    }

    public boolean equals(Object o) {
        Transition other = (Transition)o;
        return this.label.equals(other.label) &&
               this.target.equals(other.target);
    }

    public int compareTo(Object o) {
        Transition other = (Transition)o;
        return this.label.compareTo(other.label);
    }

    public String toString() {
        return label+"->"+target.stateNumber;
    }
}