| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.pig.newplan.logical.expression; |
| |
| import java.util.List; |
| |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| import org.apache.pig.newplan.Operator; |
| import org.apache.pig.newplan.OperatorPlan; |
| |
| /** |
| * Superclass for all unary expressions |
| * |
| */ |
| public abstract class UnaryExpression extends LogicalExpression { |
| |
| /** |
| * Will add this operator to the plan and connect it to the |
| * left and right hand side operators. |
| * @param name of the operator |
| * @param plan plan this operator is part of |
| * @param exp expression that this expression operators on |
| */ |
| public UnaryExpression(String name, |
| OperatorPlan plan, |
| LogicalExpression exp) { |
| super(name, plan); |
| plan.add(this); |
| plan.connect(this, exp); |
| } |
| |
| /** |
| * Get the expression that this unary expression operators on. |
| * @return expression on the left hand side |
| * @throws FrontendException |
| */ |
| public LogicalExpression getExpression() throws FrontendException { |
| List<Operator> preds = plan.getSuccessors(this); |
| if(preds == null) { |
| return null; |
| } |
| return (LogicalExpression)preds.get(0); |
| } |
| } |