| /* |
| * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Sun designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Sun in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| * CA 95054 USA or visit www.sun.com if you need additional information or |
| * have any questions. |
| */ |
| |
| package com.sun.tools.internal.xjc.reader.gbind; |
| |
| /** |
| * {@link Expression} that represents a concatanation of two expressions |
| * "A,B". |
| * |
| * @author Kohsuke Kawaguchi |
| */ |
| public final class Sequence extends Expression { |
| /** |
| * 'A' of 'A,B' |
| */ |
| private final Expression lhs; |
| /** |
| * 'B' of 'A,B' |
| */ |
| private final Expression rhs; |
| /** |
| * Compute this value eagerly for better performance |
| */ |
| private final boolean isNullable; |
| |
| /** |
| * Cached value of {@link #lastSet()} for better performance. |
| * Sequence tends to be where the recursive lastSet computation occurs. |
| */ |
| private ElementSet lastSet; |
| |
| public Sequence(Expression lhs, Expression rhs) { |
| this.lhs = lhs; |
| this.rhs = rhs; |
| isNullable = lhs.isNullable() && rhs.isNullable(); |
| } |
| |
| ElementSet lastSet() { |
| if(lastSet==null) { |
| if(rhs.isNullable()) |
| lastSet = ElementSets.union(lhs.lastSet(),rhs.lastSet()); |
| else |
| lastSet = rhs.lastSet(); |
| } |
| return lastSet; |
| } |
| |
| boolean isNullable() { |
| return isNullable; |
| } |
| |
| void buildDAG(ElementSet incoming) { |
| lhs.buildDAG(incoming); |
| if(lhs.isNullable()) |
| rhs.buildDAG(ElementSets.union(incoming,lhs.lastSet())); |
| else |
| rhs.buildDAG(lhs.lastSet()); |
| } |
| |
| public String toString() { |
| return '('+lhs.toString()+','+rhs.toString()+')'; |
| } |
| } |