#region Math.NET Iridium (LGPL) by Ruegg

// Math.NET Iridium, part of the Math.NET Project

// http://mathnet.opensourcedotnet.info

//

// Copyright (c) 2002-2008, Christoph Rüegg, http://christoph.ruegg.name

//

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published 

// by the Free Software Foundation; either version 2 of the License, or

// (at your option) any later version.

//

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU Lesser General Public License for more details.

//

// You should have received a copy of the GNU Lesser General Public 

// License along with this program; if not, write to the Free Software

// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

#endregion

#region Derived From: Copyright 2006 Troschütz

/* 

 * Derived from the Troschuetz.Random Class Library,

 * Copyright © 2006 Stefan Troschütz (stefan@troschuetz.de)

 * 

 * Troschuetz.Random is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA 

 */

#endregion



using System;

using MathNet.Numerics.RandomSources;

using MathNet.Numerics.Properties;



namespace MathNet.Numerics.Distributions

{

    /// <summary>

    /// Declares common functionality for all continuous random number

    /// distributions based on a random source.

    /// </summary>

    public abstract class ContinuousDistribution :

        IContinuousGenerator,

        IContinuousProbabilityDistribution

    {

        RandomSource _random;



        /// <summary>

        /// Initializes a new instance of the <see cref="ContinuousDistribution"/> class, using a 

        /// <see cref="SystemRandomSource"/> as underlying random number generator.

        /// </summary>

        protected

        ContinuousDistribution()

            : this(new SystemRandomSource())

        {

        }



        /// <summary>

        /// Initializes a new instance of the <see cref="ContinuousDistribution"/> class, using the

        /// specified <see cref="RandomSource"/> as underlying random number generator.

        /// </summary>

        /// <param name="random">A <see cref="RandomSource"/> object.</param>

        /// <exception cref="ArgumentNullException">

        ///     <paramref name="random"/> is NULL (<see langword="Nothing"/> in Visual Basic).

        /// </exception>

        protected

        ContinuousDistribution(

            RandomSource random

            )

        {

            if(random == null)

            {

                string message = string.Format(null, Resources.ArgumentNull, "generator");

                throw new ArgumentNullException("generator", message);

            }



            _random = random;

        }



        /// <summary>

        /// Returns a distributed floating point random number.

        /// </summary>

        /// <returns>A distributed double-precision floating point number.</returns>

        public abstract

        double

        NextDouble();



        /// <summary>

        /// Continuous probability density function (pdf) of this probability distribution.

        /// </summary>

        public abstract

        double

        ProbabilityDensity(

            double x

            );



        /// <summary>

        /// Continuous cumulative distribution function (cdf) of this probability distribution.

        /// </summary>

        public abstract

        double

        CumulativeDistribution(

            double x

            );



        /// <summary>

        /// Resets the random number distribution, so that it produces the same random number sequence again.

        /// </summary>

        public

        void

        Reset()

        {

            _random.Reset();

        }



        /// <summary>

        /// Lower limit of a random variable with this probability distribution.

        /// </summary>

        public abstract double Minimum

        {

            get;

        }



        /// <summary>

        /// Upper limit of a random variable with this probability distribution.

        /// </summary>

        public abstract double Maximum

        {

            get;

        }



        /// <summary>

        /// The expected value of a random variable with this probability distribution.

        /// </summary>

        public abstract double Mean

        {

            get;

        }



        /// <summary>

        /// The value separating the lower half part from the upper half part of a random variable with this probability distribution.

        /// </summary>

        public abstract double Median

        {

            get;

        }



        /// <summary>

        /// Average of the squared distances to the expected value of a random variable with this probability distribution.

        /// </summary>

        public abstract double Variance

        {

            get;

        }



        /// <summary>

        /// Measure of the asymmetry of this probability distribution.

        /// </summary>

        public abstract double Skewness

        {

            get;

        }



        /// <summary>

        /// Gets or sets a <see cref="RandomSource"/> object that can be used

        /// as underlying random number generator.

        /// </summary>

        public virtual RandomSource RandomSource

        {

            get { return _random; }

            set { _random = value; }

        }



        /// <summary>

        /// Gets a value indicating whether the random number distribution can be reset,

        /// so that it produces the same  random number sequence again.

        /// </summary>

        public bool CanReset

        {

            get { return _random.CanReset; }

        }

    }

}