01: /*
02: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
03: *
04: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
05: *
06: * The contents of this file are subject to the terms of either the GNU
07: * General Public License Version 2 only ("GPL") or the Common Development
08: * and Distribution License("CDDL") (collectively, the "License"). You
09: * may not use this file except in compliance with the License. You can obtain
10: * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
11: * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
12: * language governing permissions and limitations under the License.
13: *
14: * When distributing the software, include this License Header Notice in each
15: * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
16: * Sun designates this particular file as subject to the "Classpath" exception
17: * as provided by Sun in the GPL Version 2 section of the License file that
18: * accompanied this code. If applicable, add the following below the License
19: * Header, with the fields enclosed by brackets [] replaced by your own
20: * identifying information: "Portions Copyrighted [year]
21: * [name of copyright owner]"
22: *
23: * Contributor(s):
24: *
25: * If you wish your version of this file to be governed by only the CDDL or
26: * only the GPL Version 2, indicate your decision by adding "[Contributor]
27: * elects to include this software in this distribution under the [CDDL or GPL
28: * Version 2] license." If you don't indicate a single choice of license, a
29: * recipient has the option to distribute your version of this file under
30: * either the CDDL, the GPL Version 2 or to extend the choice of license to
31: * its licensees as provided above. However, if you add GPL Version 2 code
32: * and therefore, elected the GPL Version 2 license, then the option applies
33: * only if the new code is made subject to such option by the copyright
34: * holder.
35: */
36:
37: package com.sun.tools.xjc.reader.gbind;
38:
39: import java.util.Set;
40:
41: /**
42: * This builds content models.
43: *
44: * @author Kohsuke Kawaguchi
45: */
46: public abstract class Expression {
47:
48: /**
49: * Computes <tt>LAST(exp)</tt>
50: */
51: abstract ElementSet lastSet();
52:
53: /**
54: * True of <tt>\epsilon \in L(exp)</tt>
55: */
56: abstract boolean isNullable();
57:
58: /**
59: * Builds up a DAG among {@link Element}s in this expression.
60: */
61: abstract void buildDAG(ElementSet incoming);
62:
63: /**
64: * {@link Expression} that represents epsilon, the length-0 string.
65: */
66: public static final Expression EPSILON = new Expression() {
67: ElementSet lastSet() {
68: return ElementSet.EMPTY_SET;
69: }
70:
71: boolean isNullable() {
72: return true;
73: }
74:
75: void buildDAG(ElementSet incoming) {
76: // noop
77: }
78:
79: void assignElementNumber(Set<Element> allElements) {
80: // noop
81: }
82:
83: public String toString() {
84: return "-";
85: }
86: };
87: }
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