/**                                                                                                                                                                                
 * Copyright (c) 2010 Yahoo! Inc. All rights reserved.                                                                                                                             
 *                                                                                                                                                                                 
 * Licensed 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. See accompanying                                                                                                                 
 * LICENSE file.                                                                                                                                                                   
 */

package com.yahoo.ycsb.generator;

/**
 * An expression that generates a sequence of values, following some distribution (Uniform, Zipfian, Sequential, etc.)
 */
public abstract class Generator<V> 
{
	/**
	 * Generate the next value in the distribution.
	 */
	public abstract V nextValue();

	/**
	 * Return the previous value generated by the distribution; e.g., returned from the last {@link Generator#nextValue()} call. 
	 * Calling {@link #lastValue()} should not advance the distribution or have any side effects. If {@link #nextValue()} has not yet 
	 * been called, {@link #lastValue()} should return something reasonable.
	 */
	public abstract V lastValue();
	
	public final String nextString() {
	  V ret = nextValue();
	  return ret == null ? null : ret.toString();
	}
	
	public final String lastString() {
	  V ret = lastValue();
	  return ret == null ? null : ret.toString();
	}
}