text: // Copyright (C) 2008-2015 National ICT Australia (NICTA)
  // 
  // This Source Code Form is subject to the terms of the Mozilla Public
  // License, v. 2.0. If a copy of the MPL was not distributed with this
  // file, You can obtain one at http://mozilla.org/MPL/2.0/.
  // -------------------------------------------------------------------
  // 
  // Written by Conrad Sanderson - http://conradsanderson.id.au
  // Written by James Sanders
  
  
  //! \addtogroup subview
  //! @{
  
  
  //! Class for storing data required to construct or apply operations to a submatrix
  //! (i.e. where the submatrix starts and ends as well as a reference/pointer to the original matrix),
  template<typename eT>
  class subview : public Base<eT, subview<eT> >
    {
    public:
    
    typedef eT                                       elem_type;
    typedef typename get_pod_type<elem_type>::result pod_type;
    
    arma_aligned const Mat<eT>& m;
    
    static const bool is_row = false;
    static const bool is_col = false;
    
    const uword aux_row1;
    const uword aux_col1;
    
    const uword n_rows;
    const uword n_cols;
    const uword n_elem;
    
    protected:
    
    arma_inline subview(const Mat<eT>& in_m, const uword in_row1, const uword in_col1, const uword in_n_rows, const uword in_n_cols);
    
    
    public:
    
    inline ~subview();
    
    template<typename op_type             > inline void inplace_op(const eT           val                        );
    template<typename op_type, typename T1> inline void inplace_op(const Base<eT,T1>& x,   const char* identifier);
    template<typename op_type             > inline void inplace_op(const subview<eT>& x,   const char* identifier);
    
    // deliberately returning void
    
    inline void operator=  (const eT val);
    inline void operator+= (const eT val);
    inline void operator-= (const eT val);
    inline void operator*= (const eT val);
    inline void operator/= (const eT val);
    
    inline void operator=  (const subview& x);
    inline void operator+= (const subview& x);
    inline void operator-= (const subview& x);
    inline void operator%= (const subview& x);
    inline void operator/= (const subview& x);
    
    template<typename T1> inline void operator=  (const Base<eT,T1>& x);
    template<typename T1> inline void operator+= (const Base<eT,T1>& x);
    template<typename T1> inline void operator-= (const Base<eT,T1>& x);
    template<typename T1> inline void operator%= (const Base<eT,T1>& x);
    template<typename T1> inline void operator/= (const Base<eT,T1>& x);
    
    template<typename T1> inline void operator=  (const SpBase<eT,T1>& x);
    template<typename T1> inline void operator+= (const SpBase<eT,T1>& x);
    template<typename T1> inline void operator-= (const SpBase<eT,T1>& x);
    template<typename T1> inline void operator%= (const SpBase<eT,T1>& x);
    template<typename T1> inline void operator/= (const SpBase<eT,T1>& x);
  
    template<typename T1, typename gen_type>
    inline typename enable_if2< is_same_type<typename T1::elem_type, eT>::value, void>::result operator=(const Gen<T1,gen_type>& x);
    
    
    inline static void extract(Mat<eT>& out, const subview& in);
    
    inline static void  plus_inplace(Mat<eT>& out, const subview& in);
    inline static void minus_inplace(Mat<eT>& out, const subview& in);
    inline static void schur_inplace(Mat<eT>& out, const subview& in);
    inline static void   div_inplace(Mat<eT>& out, const subview& in);
    
    template<typename functor> inline void  for_each(functor F);
    template<typename functor> inline void transform(functor F);
    template<typename functor> inline void     imbue(functor F);
    
    inline void fill(const eT val);
    inline void zeros();
    inline void ones();
    inline void eye();
    inline void randu();
    inline void randn();
    
    inline eT  at_alt    (const uword ii) const;
    
    inline eT& operator[](const uword ii);
    inline eT  operator[](const uword ii) const;
    
    inline eT& operator()(const uword ii);
    inline eT  operator()(const uword ii) const;
    
    inline eT& operator()(const uword in_row, const uword in_col);
    inline eT  operator()(const uword in_row, const uword in_col) const;
    
    inline eT&         at(const uword in_row, const uword in_col);
    inline eT          at(const uword in_row, const uword in_col) const;
    
    arma_inline       eT* colptr(const uword in_col);
    arma_inline const eT* colptr(const uword in_col) const;
    
    inline bool check_overlap(const subview& x) const;
    
    inline arma_warn_unused bool is_vec()    const;
    inline arma_warn_unused bool is_finite() const;
    
    inline arma_warn_unused bool has_inf() const;
    inline arma_warn_unused bool has_nan() const;
    
    inline       subview_row<eT> row(const uword row_num);
    inline const subview_row<eT> row(const uword row_num) const;
    
    inline            subview_row<eT> operator()(const uword row_num, const span& col_span);
    inline      const subview_row<eT> operator()(const uword row_num, const span& col_span) const;
    
    inline       subview_col<eT> col(const uword col_num);
    inline const subview_col<eT> col(const uword col_num) const;
    
    inline            subview_col<eT> operator()(const span& row_span, const uword col_num);
    inline      const subview_col<eT> operator()(const span& row_span, const uword col_num) const;
    
    inline            Col<eT>  unsafe_col(const uword col_num);
    inline      const Col<eT>  unsafe_col(const uword col_num) const;
    
    inline       subview<eT> rows(const uword in_row1, const uword in_row2);
    inline const subview<eT> rows(const uword in_row1, const uword in_row2) const;
    
    inline       subview<eT> cols(const uword in_col1, const uword in_col2);
    inline const subview<eT> cols(const uword in_col1, const uword in_col2) const;
    
    inline       subview<eT> submat(const uword in_row1, const uword in_col1, const uword in_row2, const uword in_col2);
    inline const subview<eT> submat(const uword in_row1, const uword in_col1, const uword in_row2, const uword in_col2) const;
    
    inline            subview<eT> submat    (const span& row_span, const span& col_span);
    inline      const subview<eT> submat    (const span& row_span, const span& col_span) const;
    
    inline            subview<eT> operator()(const span& row_span, const span& col_span);
    inline      const subview<eT> operator()(const span& row_span, const span& col_span) const;
    
    inline subview_each1< subview<eT>, 0 > each_col();
    inline subview_each1< subview<eT>, 1 > each_row();
    
    template<typename T1> inline subview_each2< subview<eT>, 0, T1 > each_col(const Base<uword, T1>& indices);
    template<typename T1> inline subview_each2< subview<eT>, 1, T1 > each_row(const Base<uword, T1>& indices);
    
    inline       diagview<eT> diag(const sword in_id = 0);
    inline const diagview<eT> diag(const sword in_id = 0) const;
    
    inline void swap_rows(const uword in_row1, const uword in_row2);
    inline void swap_cols(const uword in_col1, const uword in_col2);
    
    
    private:
    
    friend class Mat<eT>;
    subview();
    };
  
  
  
  template<typename eT>
  class subview_col : public subview<eT>
    {
    public:
    
    typedef eT                                       elem_type;
    typedef typename get_pod_type<elem_type>::result pod_type;
    
    static const bool is_row = false;
    static const bool is_col = true;
    
    const eT* colmem;
    
    inline void operator= (const subview<eT>& x);
    inline void operator= (const subview_col& x);
    inline void operator= (const eT val);
    
    template<typename T1>
    inline void operator= (const Base<eT,T1>& x);
    
    template<typename T1, typename gen_type>
    inline typename enable_if2< is_same_type<typename T1::elem_type, eT>::value, void>::result operator=(const Gen<T1,gen_type>& x);
    
    arma_inline const Op<subview_col<eT>,op_htrans>  t() const;
    arma_inline const Op<subview_col<eT>,op_htrans> ht() const;
    arma_inline const Op<subview_col<eT>,op_strans> st() const;
    
    inline void fill(const eT val);
    inline void zeros();
    inline void ones();
    
    arma_inline eT  at_alt    (const uword i) const;
    
    arma_inline eT& operator[](const uword i);
    arma_inline eT  operator[](const uword i) const;
    
    inline eT& operator()(const uword i);
    inline eT  operator()(const uword i) const;
    
    inline eT& operator()(const uword in_row, const uword in_col);
    inline eT  operator()(const uword in_row, const uword in_col) const;
    
    inline eT&         at(const uword in_row, const uword in_col);
    inline eT          at(const uword in_row, const uword in_col) const;
    
    arma_inline       eT* colptr(const uword in_col);
    arma_inline const eT* colptr(const uword in_col) const;
    
    inline       subview_col<eT> rows(const uword in_row1, const uword in_row2);
    inline const subview_col<eT> rows(const uword in_row1, const uword in_row2) const;
    
    inline       subview_col<eT> subvec(const uword in_row1, const uword in_row2);
    inline const subview_col<eT> subvec(const uword in_row1, const uword in_row2) const;
    
    inline       subview_col<eT> head(const uword N);
    inline const subview_col<eT> head(const uword N) const;
    
    inline       subview_col<eT> tail(const uword N);
    inline const subview_col<eT> tail(const uword N) const;
    
    
    protected:
    
    inline subview_col(const Mat<eT>& in_m, const uword in_col);
    inline subview_col(const Mat<eT>& in_m, const uword in_col, const uword in_row1, const uword in_n_rows);
    
    
    private:
    
    friend class Mat<eT>;
    friend class Col<eT>;
    friend class subview<eT>;
    
    subview_col();
    };
  
  
  
  template<typename eT>
  class subview_row : public subview<eT>
    {
    public:
    
    typedef eT                                       elem_type;
    typedef typename get_pod_type<elem_type>::result pod_type;
    
    static const bool is_row = true;
    static const bool is_col = false;
    
    inline void operator= (const subview<eT>& x);
    inline void operator= (const subview_row& x);
    inline void operator= (const eT val);
    
    template<typename T1>
    inline void operator= (const Base<eT,T1>& x);
    
    template<typename T1, typename gen_type>
    inline typename enable_if2< is_same_type<typename T1::elem_type, eT>::value, void>::result operator=(const Gen<T1,gen_type>& x);
    
    arma_inline const Op<subview_row<eT>,op_htrans>  t() const;
    arma_inline const Op<subview_row<eT>,op_htrans> ht() const;
    arma_inline const Op<subview_row<eT>,op_strans> st() const;
    
    inline eT  at_alt    (const uword i) const;
    
    inline eT& operator[](const uword i);
    inline eT  operator[](const uword i) const;
    
    inline eT& operator()(const uword i);
    inline eT  operator()(const uword i) const;
    
    inline eT& operator()(const uword in_row, const uword in_col);
    inline eT  operator()(const uword in_row, const uword in_col) const;
    
    inline eT&         at(const uword in_row, const uword in_col);
    inline eT          at(const uword in_row, const uword in_col) const;
    
    inline       subview_row<eT> cols(const uword in_col1, const uword in_col2);
    inline const subview_row<eT> cols(const uword in_col1, const uword in_col2) const;
    
    inline       subview_row<eT> subvec(const uword in_col1, const uword in_col2);
    inline const subview_row<eT> subvec(const uword in_col1, const uword in_col2) const;
    
    inline       subview_row<eT> head(const uword N);
    inline const subview_row<eT> head(const uword N) const;
    
    inline       subview_row<eT> tail(const uword N);
    inline const subview_row<eT> tail(const uword N) const;
    
    
    protected:
    
    inline subview_row(const Mat<eT>& in_m, const uword in_row);
    inline subview_row(const Mat<eT>& in_m, const uword in_row, const uword in_col1, const uword in_n_cols);
    
    
    private:
    
    friend class Mat<eT>;
    friend class Row<eT>;
    friend class subview<eT>;
    
    subview_row();
    };
  
  
  
  template<typename eT>
  class subview_row_strans : public Base<eT, subview_row_strans<eT> >
    {
    public:
    
    typedef eT                                       elem_type;
    typedef typename get_pod_type<elem_type>::result pod_type;
    
    static const bool is_row = false;
    static const bool is_col = true;
    
    arma_aligned const subview_row<eT>& sv_row;
    
           const uword n_rows;     // equal to n_elem
           const uword n_elem;
    static const uword n_cols = 1;
    
    
    inline explicit subview_row_strans(const subview_row<eT>& in_sv_row);
    
    inline void extract(Mat<eT>& out) const;
    
    inline eT  at_alt    (const uword i) const;
    
    inline eT  operator[](const uword i) const;
    inline eT  operator()(const uword i) const;
    
    inline eT  operator()(const uword in_row, const uword in_col) const;
    inline eT          at(const uword in_row, const uword in_col) const;
    };
  
  
  
  template<typename eT>
  class subview_row_htrans : public Base<eT, subview_row_htrans<eT> >
    {
    public:
    
    typedef eT                                       elem_type;
    typedef typename get_pod_type<elem_type>::result pod_type;
    
    static const bool is_row = false;
    static const bool is_col = true;
    
    arma_aligned const subview_row<eT>& sv_row;
    
           const uword n_rows;     // equal to n_elem
           const uword n_elem;
    static const uword n_cols = 1;
    
    
    inline explicit subview_row_htrans(const subview_row<eT>& in_sv_row);
    
    inline void extract(Mat<eT>& out) const;
    
    inline eT  at_alt    (const uword i) const;
    
    inline eT  operator[](const uword i) const;
    inline eT  operator()(const uword i) const;
    
    inline eT  operator()(const uword in_row, const uword in_col) const;
    inline eT          at(const uword in_row, const uword in_col) const;
    };
  
  
  
  //! @}
  