1 /* 2 * [The "BSD license"] 3 * Copyright (c) 2010 Terence Parr 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 package org.antlr.analysis; 29 30 /** A generic transition between any two state machine states. It defines 31 * some special labels that indicate things like epsilon transitions and 32 * that the label is actually a set of labels or a semantic predicate. 33 * This is a one way link. It emanates from a state (usually via a list of 34 * transitions) and has a label/target pair. I have abstracted the notion 35 * of a Label to handle the various kinds of things it can be. 36 */ 37 public class Transition implements Comparable<Transition> { 38 /** What label must be consumed to transition to target */ 39 public Label label; 40 41 /** The target of this transition */ 42 public State target; 43 Transition(Label label, State target)44 public Transition(Label label, State target) { 45 this.label = label; 46 this.target = target; 47 } 48 Transition(int label, State target)49 public Transition(int label, State target) { 50 this.label = new Label(label); 51 this.target = target; 52 } 53 isEpsilon()54 public boolean isEpsilon() { 55 return label.isEpsilon(); 56 } 57 isAction()58 public boolean isAction() { 59 return label.isAction(); 60 } 61 isSemanticPredicate()62 public boolean isSemanticPredicate() { 63 return label.isSemanticPredicate(); 64 } 65 66 @Override hashCode()67 public int hashCode() { 68 return label.hashCode() + target.stateNumber; 69 } 70 71 @Override equals(Object o)72 public boolean equals(Object o) { 73 Transition other = (Transition)o; 74 return this.label.equals(other.label) && 75 this.target.equals(other.target); 76 } 77 78 @Override compareTo(Transition other)79 public int compareTo(Transition other) { 80 return this.label.compareTo(other.label); 81 } 82 83 @Override toString()84 public String toString() { 85 return label+"->"+target.stateNumber; 86 } 87 } 88