Function diagonal

Externals/eigen/Eigen/src/SparseCore/SparseMatrix.h:626–626

\returns a const expression of the diagonal coefficients */

    /** \returns a const expression of the diagonal coefficients */
    const Diagonal<const SparseMatrix> diagonal() const { return *this; }

    /** Default constructor yielding an empty \c 0 \c x \c 0 matrix */
    inline SparseMatrix()