Uniform.h

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/*!
 * 
 *
 * \brief       Implements a uniform distribution.
 * 
 * 
 *
 * \author      O. Krause
 * \date        2010-01-01
 *
 *
 * \par Copyright 1995-2017 Shark Development Team
 * 
 * <BR><HR>
 * This file is part of Shark.
 * <http://shark-ml.org/>
 * 
 * Shark 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 3 of the License, or
 * (at your option) any later version.
 * 
 * Shark 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 Shark.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#ifndef SHARK_RNG_UNIFORM_H
#define SHARK_RNG_UNIFORM_H

#include "shark/Rng/AbstractDistribution.h"
#include "shark/Rng/Rng.h"

#include <boost/random.hpp>

namespace shark{

/**
* \brief Implements a continuous uniform distribution.
*/
template<typename RngType = DefaultRngType>
class Uniform
:
    public AbstractDistribution,
    public boost::variate_generator<RngType*,boost::uniform_real<> >
{
private:

    typedef boost::variate_generator<RngType*,boost::uniform_real<> > Base;

public:

    /**
    * \brief Default c'tor. Initializes the sampling interval and associates
    * this distribution with the supplied RNG.
    * \param [in,out] rng The RNG to associate this distribution with.
    * \param [in] low_ The lower bound of the sampling interval.
    * \param [in] high_ The upper bound of the sampling interval.
    */
    Uniform( RngType & rng, double low_ = 0., double high_ = 1. )
        :Base(&rng,boost::uniform_real<>(std::min(low_,high_),std::max(low_,high_)))
    {}

    /**
    * \brief Injects the default sampling operator.
    */
    using Base::operator();

    /**
    * \brief Resets the distribution to the supplied interval and samples a random number.
    * \param [in] low_ The lower bound of the interval.
    * \param [in] high_ The upper bound of the interval.
    */
    double operator()(double low_,double high_)
    {
        if(low_ == high_) return low_;
        boost::uniform_real<> dist( std::min(low_,high_), std::max( high_, low_ ) );
        return dist(Base::engine());
    }

    /**
    * \brief Accesses the lower bound of the interval.
    */
    double low()const
    {
        return Base::distribution().min();
    }

    /**
    * \brief Accesses the upper bound of the interval.
    */
    double high()const
    {
        return Base::distribution().max();
    }

    /**
    * \brief Adjusts the interval of the distribution.
    * \param [in] low_ The lower bound of the interval.
    * \param [in] high_ The upper bound of the interval.
    */
    void setRange(double low_,double high_)
    {
        boost::uniform_real<> dist(std::min(low_,high_),std::max(low_,high_));
        Base::distribution()=dist;
    }

    /**
    * \brief Calculates the probability of x.
    * \param [in] x The observation.
    */
    double p(double x) const {
        return x >= low() && x < high() ? 1 / (high() - low()) : 0;
    }
};

///\brief Draws a number uniformly in [lower,upper] by drawing random numbers from rng.
template<class RngType>
double uni(RngType& rng, double lower, double upper){
    Uniform<RngType> dist(rng, lower, upper);
    return dist();
}

} // namespace shark {

#endif // SHARK_RNG_UNIFORM_H