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: /**
40: * {@link Expression} that represents a concatanation of two expressions
41: * "A,B".
42: *
43: * @author Kohsuke Kawaguchi
44: */
45: public final class Sequence extends Expression {
46: /**
47: * 'A' of 'A,B'
48: */
49: private final Expression lhs;
50: /**
51: * 'B' of 'A,B'
52: */
53: private final Expression rhs;
54: /**
55: * Compute this value eagerly for better performance
56: */
57: private final boolean isNullable;
58:
59: /**
60: * Cached value of {@link #lastSet()} for better performance.
61: * Sequence tends to be where the recursive lastSet computation occurs.
62: */
63: private ElementSet lastSet;
64:
65: public Sequence(Expression lhs, Expression rhs) {
66: this .lhs = lhs;
67: this .rhs = rhs;
68: isNullable = lhs.isNullable() && rhs.isNullable();
69: }
70:
71: ElementSet lastSet() {
72: if (lastSet == null) {
73: if (rhs.isNullable())
74: lastSet = ElementSets.union(lhs.lastSet(), rhs
75: .lastSet());
76: else
77: lastSet = rhs.lastSet();
78: }
79: return lastSet;
80: }
81:
82: boolean isNullable() {
83: return isNullable;
84: }
85:
86: void buildDAG(ElementSet incoming) {
87: lhs.buildDAG(incoming);
88: if (lhs.isNullable())
89: rhs.buildDAG(ElementSets.union(incoming, lhs.lastSet()));
90: else
91: rhs.buildDAG(lhs.lastSet());
92: }
93:
94: public String toString() {
95: return '(' + lhs.toString() + ',' + rhs.toString() + ')';
96: }
97: }
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