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/**
 * 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.hadoop.hive.ql.lib;

import java.util.Stack;

import org.apache.hadoop.hive.ql.parse.SemanticException;

/**
 * Rule interface for Operators Used in operator dispatching to dispatch
 * process/visitor functions for operators.
 */
public interface Rule {

  /**
   * @return the cost of the rule - the lower the cost, the better the rule
   *         matches
   * @throws SemanticException
   */
  int cost(Stack stack) throws SemanticException;

  /**
   * @return the name of the rule - may be useful for debugging
   */
  String getName();
}