core/src/main/java/org/apache/mrql/Function.java

/**
 * 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.mrql;

import java.io.*;


/**
 * An anonymous function from MRData to MRData (a lambda abstraction)
 * Must provide a concrete implementation for eval (the lambda body)
 */
abstract public class Function implements Serializable {
    /**
     * Evaluate the anonymous function from MRData to MRData
     * @param arg the operand to be evaluated
     * @return the result of evaluating
     */
    abstract public MRData eval ( final MRData arg );
}