Rating.h

//-----------------------------------------------------------------------------
/** @file libboardgame_base/Rating.h
    @author Markus Enzenberger
    @copyright GNU General Public License version 3 or later */
//-----------------------------------------------------------------------------

#ifndef LIBBOARDGAME_BASE_RATING_H
#define LIBBOARDGAME_BASE_RATING_H

#include <cmath>
#include <iosfwd>

namespace libboardgame_base {

using namespace std;

//-----------------------------------------------------------------------------

/** Elo-rating of a player. */
class Rating
{
public:
    friend ostream& operator<<(ostream& out, Rating rating);
    friend istream& operator>>(istream& in, Rating& rating);

    explicit Rating(double elo = 0) : m_elo(elo) { }

    /** Get the expected outcome of a game.
        @param elo_opponent Elo-rating of the opponent.
        @param nu_opponents The number of opponents (all with the same rating
        elo_opponent) */
    double get_expected_result(Rating elo_opponent,
                               unsigned nu_opponents = 1) const;

    /** Update a rating after a game.
        @param game_result The outcome of the game (0=loss, 0.5=tie, 1=win)
        @param elo_opponent Elo-rating of the opponent.
        @param k_value The K-value
        @param nu_opponents The number of opponents (all with the same rating
        elo_opponent) */
    void update(double game_result, Rating elo_opponent, double k_value = 32,
                unsigned nu_opponents = 1);

    double get() const { return m_elo; }

private:
    double m_elo;
};

//-----------------------------------------------------------------------------

} // namespace libboardgame_base

#endif // LIBBOARDGAME_BASE_RATING_H