/*
    Scan Tailor - Interactive post-processing tool for scanned pages.
    Copyright (C)  Joseph Artsimovich <joseph.artsimovich@gmail.com>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef LINEAR_FUNCTION_H_
#define LINEAR_FUNCTION_H_

#include "VecT.h"
#include <stddef.h>

/**
 * A linear function from arbitrary number of variables
 * expressed in matrix form:
 * \code
 * F(x) = a^T * x + b
 * \endcode
 */
class LinearFunction
{
    // Member-wise copying is OK.
public:
    VecT<double> a;
    double b;

    /**
     * Constructs a linear function of the given number of variables,
     * initializing everything to zero.
     */
    LinearFunction(size_t num_vars = 0);

    /**
     * Resets everything to zero, so that F(x) = 0
     */
    void reset();

    size_t numVars() const
    {
        return a.size();
    }

    /**
     * Evaluates a^T * x + b
     */
    double evaluate(double const* x) const;

    void swap(LinearFunction& other);

    LinearFunction& operator+=(LinearFunction const& other);

    LinearFunction& operator*=(double scalar);
};

inline void swap(LinearFunction& f1, LinearFunction& f2)
{
    f1.swap(f2);
}

#endif
