001: /* ====================================================================
002: * Tea - Copyright (c) 1997-2000 Walt Disney Internet Group
003: * ====================================================================
004: * The Tea Software License, Version 1.1
005: *
006: * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
007: *
008: * Redistribution and use in source and binary forms, with or without
009: * modification, are permitted provided that the following conditions
010: * are met:
011: *
012: * 1. Redistributions of source code must retain the above copyright
013: * notice, this list of conditions and the following disclaimer.
014: *
015: * 2. Redistributions in binary form must reproduce the above copyright
016: * notice, this list of conditions and the following disclaimer in
017: * the documentation and/or other materials provided with the
018: * distribution.
019: *
020: * 3. The end-user documentation included with the redistribution,
021: * if any, must include the following acknowledgment:
022: * "This product includes software developed by the
023: * Walt Disney Internet Group (http://opensource.go.com/)."
024: * Alternately, this acknowledgment may appear in the software itself,
025: * if and wherever such third-party acknowledgments normally appear.
026: *
027: * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
028: * not be used to endorse or promote products derived from this
029: * software without prior written permission. For written
030: * permission, please contact opensource@dig.com.
031: *
032: * 5. Products derived from this software may not be called "Tea",
033: * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
034: * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
035: * written permission of the Walt Disney Internet Group.
036: *
037: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
038: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
039: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
040: * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
041: * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
042: * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
043: * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
044: * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
045: * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
046: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
047: * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
048: * ====================================================================
049: *
050: * For more information about Tea, please see http://opensource.go.com/.
051: */
052:
053: package com.go.tea.parsetree;
054:
055: import com.go.tea.compiler.SourceInfo;
056: import com.go.tea.compiler.Token;
057:
058: /******************************************************************************
059: * RelationalExpression defines seven operations, "==", "!=", "<", ">", "<="
060: * ">=" and "isa". The type of a RelationalExpression is a Boolean, set by a
061: * type checker if there are no errors.
062: *
063: * <p>Operator returned is one of Token.EQ, Token.NE, Token.LT, Token.GT,
064: * Token.LE, Token.GE or Token.ISA.
065: *
066: * @author Brian S O'Neill
067: * @version
068: * <!--$$Revision:--> 25 <!-- $-->, <!--$$JustDate:--> 9/07/00 <!-- $-->
069: */
070: public class RelationalExpression extends BinaryLogicalExpression {
071: private TypeName mTypeName;
072:
073: public RelationalExpression(SourceInfo info, Token operator,
074: Expression left, Expression right) {
075: super (info, operator, left, right);
076: }
077:
078: /**
079: * Used to construct an "isa" RelationalExpression.
080: */
081: public RelationalExpression(SourceInfo info, Token operator,
082: Expression left, TypeName typeName) {
083: super (info, operator, left, null);
084: mTypeName = typeName;
085: }
086:
087: public Object accept(NodeVisitor visitor) {
088: return visitor.visit(this );
089: }
090:
091: public boolean isExceptionPossible() {
092: int id = getOperator().getID();
093: if (id != Token.EQ && id != Token.NE && id != Token.ISA) {
094: return super .isExceptionPossible();
095: }
096:
097: Expression left = getLeftExpression();
098: Expression right = getLeftExpression();
099:
100: return (left != null && left.isExceptionPossible())
101: || (right != null && right.isExceptionPossible());
102: }
103:
104: /**
105: * @return null if an "isa" RelationalExpression
106: */
107: public Expression getRightExpression() {
108: return super .getRightExpression();
109: }
110:
111: /**
112: * Only applies if token is "isa".
113: */
114: public TypeName getIsaTypeName() {
115: return mTypeName;
116: }
117: }
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