ExponentialDistribution.hpp

/*
 * (c) Copyright 2020 CORSIKA Project, corsika-project@lists.kit.edu
 *
 * This software is distributed under the terms of the GNU General Public
 * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
 * the license.
 */

#pragma once

#include <corsika/framework/core/PhysicalUnits.hpp>
#include <random>

namespace corsika {

  template <typename Quantity>
  class ExponentialDistribution {
    static_assert(is_quantity_v<Quantity>, "usable only with Quantity types");

    typedef typename Quantity::value_type real_type;
    typedef std::exponential_distribution<real_type> distribution_type;

  public:
    typedef Quantity value_type;

    ExponentialDistribution() = delete;

    ExponentialDistribution(value_type beta)
        : beta_(beta) {}

    ExponentialDistribution(ExponentialDistribution<value_type> const& other)
        : beta_(other.getBeta()) {}

    ExponentialDistribution<value_type>& operator=(
        ExponentialDistribution<value_type> const& other) {
      if (this == &other) return *this;
      beta_ = other.getBeta();
      return *this;
    }

    value_type getBeta() const { return beta_; }

    void setBeta(value_type const& beta) { beta_ = beta; }

    template <class Generator>
    value_type operator()(Generator& g) {
      return beta_ * dist_(g);
    }

  private:
    distribution_type dist_{1.};
    value_type beta_;
  };

} // namespace corsika