public:

typedef typename traits::storage_type<RTYPE>::type value_type ;

typedef typename Mat::iterator iterator;

typedef typename Mat::const_iterator const_iterator;

typedef typename Mat::Proxy Proxy ;

MatrixColumn( Mat& mat_, int i) : mat(mat_), index(i), n(mat.nrow()){}

MatrixColumn& operator=( const MatrixColumn& other ){

if( &other != this ){

std::copy( other.begin(), other.end(), begin() );

}

return *this ;

}

template <typename eT, typename Expr>

MatrixColumn& operator=( const SugarVectorExpression<eT, Expr>& expr ){

if( expr.size() != size() )

stop("incompatible number of elements, expecting '%d', got '%d'", size(), expr.size() );

expr.apply(*this) ;

return *this;

}

inline int size() const { return n ;}

inline Proxy operator[]( int i){ return mat[ index*n + i] ; }

inline const Proxy operator[]( int i) const { return mat[ index*n + i] ; }

inline iterator begin() { return mat.begin() + index * n ; }

inline iterator end(){ return mat.begin() + (index+1)* n ; }

inline const_iterator begin() const { return mat.begin() + index * n ; }

inline const_iterator end() const { return mat.begin() + (index+1)* n ; }

private:

Mat& mat ;

int index ;

int n ;