/*
 * 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.commons.math.distribution;

import java.io.Serializable;

import org.apache.commons.math.MathException;
import org.apache.commons.math.MathRuntimeException;

/**
 * Base class for probability distributions.
 * 
 * @version $Revision$ $Date$
 */
public abstract class AbstractDistribution implements Distribution, Serializable {

	/** Serializable version identifier */
	private static final long serialVersionUID = -38038050983108802L;

	/**
	 * Default constructor.
	 */
	protected AbstractDistribution() {
		super();
	}

	/**
	 * For a random variable X whose values are distributed according to this
	 * distribution, this method returns P(x0 &le; X &le; x1).
	 * <p>
	 * The default implementation uses the identity
	 * </p>
	 * <p>
	 * P(x0 &le; X &le; x1) = P(X &le; x1) - P(X &le; x0)
	 * </p>
	 * 
	 * @param x0
	 *            the (inclusive) lower bound
	 * @param x1
	 *            the (inclusive) upper bound
	 * @return the probability that a random variable with this distribution
	 *         will take a value between <code>x0</code> and <code>x1</code>,
	 *         including the endpoints.
	 * @throws MathException
	 *             if the cumulative probability can not be computed due to
	 *             convergence or other numerical errors.
	 * @throws IllegalArgumentException
	 *             if <code>x0 > x1</code>
	 */
	public double cumulativeProbability(double x0, double x1) throws MathException {
		if (x0 > x1) {
			throw MathRuntimeException.createIllegalArgumentException(
					"lower endpoint ({0}) must be less than or equal to upper endpoint ({1})", x0, x1);
		}
		return cumulativeProbability(x1) - cumulativeProbability(x0);
	}
}
