matrix_diagonal_product.h

// Description: Matrix diagonal product
// Documentation: matrix_algorithms.txt

#ifndef PASTELMATH_MATRIX_DIAGONAL_PRODUCT_H
#define PASTELMATH_MATRIX_DIAGONAL_PRODUCT_H

#include "pastel/math/matrix/matrix.h"

#include <algorithm>

namespace Pastel
{

    //! Returns the product of the diagonal elements.
    /*!
   returns:
   The diagonal product, if the matrix is not empty,
   (Real)Nan() otherwise.
   */
    template <typename Real, int M, int N>
    Real diagonalProduct(
        const Matrix<Real, M, N>& matrix)
    {
        integer n = matrix.cols();
        integer m = matrix.rows();
        integer minSize = std::min(n, m);

        if (minSize == 0)
        {
            return (Real)Nan();
        }

        Real result = matrix(0, 0);
        for (integer i = 1;i < minSize;++i)
        {

            result *= matrix(i, i);
        }

        return result;
    }

}

#endif