01: /*
02: [The "BSD licence"]
03: Copyright (c) 2005-2006 Terence Parr
04: All rights reserved.
05:
06: Redistribution and use in source and binary forms, with or without
07: modification, are permitted provided that the following conditions
08: are met:
09: 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 {
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:
44: public Transition(Label label, State target) {
45: this .label = label;
46: this .target = target;
47: }
48:
49: public Transition(int label, State target) {
50: this .label = new Label(label);
51: this .target = target;
52: }
53:
54: public boolean isEpsilon() {
55: return label.isEpsilon();
56: }
57:
58: public boolean isSemanticPredicate() {
59: return label.isSemanticPredicate();
60: }
61:
62: public int hashCode() {
63: return label.hashCode() + target.stateNumber;
64: }
65:
66: public boolean equals(Object o) {
67: Transition other = (Transition) o;
68: return this .label.equals(other.label)
69: && this .target.equals(other.target);
70: }
71:
72: public int compareTo(Object o) {
73: Transition other = (Transition) o;
74: return this .label.compareTo(other.label);
75: }
76:
77: public String toString() {
78: return label + "->" + target.stateNumber;
79: }
80: }
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