multinomial.h

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#ifndef META_STATS_MULTINOMIAL_H_
#define META_STATS_MULTINOMIAL_H_

#include <cstdint>
#include <random>
#include "stats/dirichlet.h"
#include "util/sparse_vector.h"

namespace meta
{
namespace stats
{

template <class T>
class multinomial
{
  public:
    using event_type = T;

    multinomial();

    multinomial(dirichlet<T> prior);

    void increment(const T& event, double count);

    void decrement(const T& event, double count);

    double counts(const T& event) const;

    double counts() const;

    template <class Fun>
    void each_seen_event(Fun&& fun) const;

    void clear();

    double probability(const T& event) const;

    const dirichlet<T>& prior() const;

    template <class Generator>
    const T& operator()(Generator&& gen) const;

    multinomial<T>& operator+=(const multinomial<T>& other);

  private:
    util::sparse_vector<T, double> counts_;
    double total_counts_;
    dirichlet<T> prior_;
};

template <class T>
multinomial<T> operator+(const multinomial<T>& lhs, const multinomial<T>& rhs)
{
    multinomial<T> res{lhs};
    res += rhs;
    return res;
}

template <class T>
multinomial<T> operator+(multinomial<T>&& lhs, const multinomial<T>& rhs)
{
    return lhs += rhs;
}

template <class T>
multinomial<T> operator+(const multinomial<T>& lhs, multinomial<T>&& rhs)
{
    return rhs += lhs;
}

template <class T>
multinomial<T> operator+(multinomial<T>&& lhs, multinomial<T>&& rhs)
{
    return lhs += rhs;
}

}
}
#include "stats/multinomial.tcc"
#endif