Chris@49: // Copyright (C) 2008-2012 NICTA (www.nicta.com.au)
Chris@49: // Copyright (C) 2008-2012 Conrad Sanderson
Chris@49: // 
Chris@49: // This Source Code Form is subject to the terms of the Mozilla Public
Chris@49: // License, v. 2.0. If a copy of the MPL was not distributed with this
Chris@49: // file, You can obtain one at http://mozilla.org/MPL/2.0/.
Chris@49: 
Chris@49: 
Chris@49: //! \addtogroup diagmat_proxy
Chris@49: //! @{
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy_default
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef typename T1::elem_type                   elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_default(const T1& X)
Chris@49:     : P       ( X )
Chris@49:     , P_is_vec( (resolves_to_vector<T1>::value) || (P.get_n_rows() == 1) || (P.get_n_cols() == 1) )
Chris@49:     , P_is_col( T1::is_col || (P.get_n_cols() == 1) )
Chris@49:     , n_elem  ( P_is_vec ? P.get_n_elem() : (std::min)(P.get_n_elem(), P.get_n_rows()) )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (P.get_n_rows() != P.get_n_cols()),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   arma_inline
Chris@49:   elem_type
Chris@49:   operator[](const uword i) const
Chris@49:     {
Chris@49:     if(Proxy<T1>::prefer_at_accessor == false)
Chris@49:       {
Chris@49:       return P_is_vec ? P[i] : P.at(i,i);
Chris@49:       }
Chris@49:     else
Chris@49:       {
Chris@49:       if(P_is_vec)
Chris@49:         {
Chris@49:         return (P_is_col) ? P.at(i,0) : P.at(0,i);
Chris@49:         }
Chris@49:       else
Chris@49:         {
Chris@49:         return P.at(i,i);
Chris@49:         }
Chris@49:       }
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   arma_inline
Chris@49:   elem_type
Chris@49:   at(const uword row, const uword col) const
Chris@49:     {
Chris@49:     if(row == col)
Chris@49:       {
Chris@49:       if(Proxy<T1>::prefer_at_accessor == false)
Chris@49:         {
Chris@49:         return (P_is_vec) ? P[row] : P.at(row,row);
Chris@49:         }
Chris@49:       else
Chris@49:         {
Chris@49:         if(P_is_vec)
Chris@49:           {
Chris@49:           return (P_is_col) ? P.at(row,0) : P.at(0,row);
Chris@49:           }
Chris@49:         else
Chris@49:           {
Chris@49:           return P.at(row,row);
Chris@49:           }
Chris@49:         }
Chris@49:       }
Chris@49:     else
Chris@49:       {
Chris@49:       return elem_type(0);
Chris@49:       }
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   const Proxy<T1> P;
Chris@49:   const bool      P_is_vec;
Chris@49:   const bool      P_is_col;
Chris@49:   const uword     n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy_fixed
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef typename T1::elem_type                   elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_fixed(const T1& X)
Chris@49:     : P(X)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (T1::n_rows != T1::n_cols),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   arma_inline
Chris@49:   elem_type
Chris@49:   operator[](const uword i) const
Chris@49:     {
Chris@49:     return (P_is_vec) ? P[i] : P.at(i,i);
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   arma_inline
Chris@49:   elem_type
Chris@49:   at(const uword row, const uword col) const
Chris@49:     {
Chris@49:     if(row == col)
Chris@49:       {
Chris@49:       return (P_is_vec) ? P[row] : P.at(row,row);
Chris@49:       }
Chris@49:     else
Chris@49:       {
Chris@49:       return elem_type(0);
Chris@49:       }
Chris@49:     }
Chris@49:   
Chris@49:   const T1& P;
Chris@49:   
Chris@49:   static const bool  P_is_vec = (T1::n_rows == 1) || (T1::n_cols == 1);
Chris@49:   static const uword n_elem   = P_is_vec ? T1::n_elem : ( (T1::n_elem < T1::n_rows) ? T1::n_elem : T1::n_rows );
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1, bool condition>
Chris@49: struct diagmat_proxy_redirect {};
Chris@49: 
Chris@49: template<typename T1>
Chris@49: struct diagmat_proxy_redirect<T1, false> { typedef diagmat_proxy_default<T1> result; };
Chris@49: 
Chris@49: template<typename T1>
Chris@49: struct diagmat_proxy_redirect<T1, true>  { typedef diagmat_proxy_fixed<T1>   result; };
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy : public diagmat_proxy_redirect<T1, is_Mat_fixed<T1>::value >::result
Chris@49:   {
Chris@49:   public:
Chris@49:   inline diagmat_proxy(const T1& X)
Chris@49:     : diagmat_proxy_redirect< T1, is_Mat_fixed<T1>::value >::result(X)
Chris@49:     {
Chris@49:     }
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy< Mat<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy(const Mat<eT>& X)
Chris@49:     : P       ( X )
Chris@49:     , P_is_vec( (X.n_rows == 1) || (X.n_cols == 1) )
Chris@49:     , n_elem  ( P_is_vec ? X.n_elem : (std::min)(X.n_elem, X.n_rows) )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (P.n_rows != P.n_cols),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P_is_vec ? P[i] : P.at(i,i);                                         }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? ( P_is_vec ? P[row] : P.at(row,row) ) : elem_type(0); }
Chris@49:   
Chris@49:   const Mat<eT>& P;
Chris@49:   const bool     P_is_vec;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy< Row<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy(const Row<eT>& X)
Chris@49:     : P(X)
Chris@49:     , n_elem(X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                                                }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Row<eT>& P;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy< Col<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy(const Col<eT>& X)
Chris@49:     : P(X)
Chris@49:     , n_elem(X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Col<eT>& P;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy< subview_row<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy(const subview_row<eT>& X)
Chris@49:     : P(X)
Chris@49:     , n_elem(X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const subview_row<eT>& P;
Chris@49:   const uword            n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy< subview_col<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy(const subview_col<eT>& X)
Chris@49:     : P(X)
Chris@49:     , n_elem(X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const subview_col<eT>& P;
Chris@49:   const uword            n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: //
Chris@49: //
Chris@49: //
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy_check_default
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef typename T1::elem_type                   elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check_default(const T1& X, const Mat<typename T1::elem_type>&)
Chris@49:     : P(X)
Chris@49:     , P_is_vec( (resolves_to_vector<T1>::value) || (P.n_rows == 1) || (P.n_cols == 1) )
Chris@49:     , n_elem( P_is_vec ? P.n_elem : (std::min)(P.n_elem, P.n_rows) )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (P.n_rows != P.n_cols),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P_is_vec ? P[i] : P.at(i,i);                                         }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? ( P_is_vec ? P[row] : P.at(row,row) ) : elem_type(0); }
Chris@49:   
Chris@49:   const Mat<elem_type> P;
Chris@49:   const bool           P_is_vec;
Chris@49:   const uword          n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy_check_fixed
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef typename T1::elem_type                   eT;
Chris@49:   typedef typename T1::elem_type                   elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check_fixed(const T1& X, const Mat<eT>& out)
Chris@49:     : P( const_cast<eT*>(X.memptr()), T1::n_rows, T1::n_cols, (&X == &out), false )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (T1::n_rows != T1::n_cols),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   
Chris@49:   arma_inline eT operator[] (const uword i)                    const { return P_is_vec ? P[i] : P.at(i,i);                                         }
Chris@49:   arma_inline eT at         (const uword row, const uword col) const { return (row == col) ? ( P_is_vec ? P[row] : P.at(row,row) ) : elem_type(0); }
Chris@49:   
Chris@49:   const Mat<eT> P;  // TODO: why not just store X directly as T1& ?  test with fixed size vectors and matrices
Chris@49:   
Chris@49:   static const bool  P_is_vec = (T1::n_rows == 1) || (T1::n_cols == 1);
Chris@49:   static const uword n_elem   = P_is_vec ? T1::n_elem : ( (T1::n_elem < T1::n_rows) ? T1::n_elem : T1::n_rows );
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename T1, bool condition>
Chris@49: struct diagmat_proxy_check_redirect {};
Chris@49: 
Chris@49: template<typename T1>
Chris@49: struct diagmat_proxy_check_redirect<T1, false> { typedef diagmat_proxy_check_default<T1> result; };
Chris@49: 
Chris@49: template<typename T1>
Chris@49: struct diagmat_proxy_check_redirect<T1, true>  { typedef diagmat_proxy_check_fixed<T1>   result; };
Chris@49: 
Chris@49: 
Chris@49: template<typename T1>
Chris@49: class diagmat_proxy_check : public diagmat_proxy_check_redirect<T1, is_Mat_fixed<T1>::value >::result
Chris@49:   {
Chris@49:   public:
Chris@49:   inline diagmat_proxy_check(const T1& X, const Mat<typename T1::elem_type>& out)
Chris@49:     : diagmat_proxy_check_redirect< T1, is_Mat_fixed<T1>::value >::result(X, out)
Chris@49:     {
Chris@49:     }
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy_check< Mat<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check(const Mat<eT>& X, const Mat<eT>& out)
Chris@49:     : P_local ( (&X == &out) ? new Mat<eT>(X) : 0  )
Chris@49:     , P       ( (&X == &out) ? (*P_local)     : X  )
Chris@49:     , P_is_vec( (P.n_rows == 1) || (P.n_cols == 1) )
Chris@49:     , n_elem  ( P_is_vec ? P.n_elem : (std::min)(P.n_elem, P.n_rows) )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     
Chris@49:     arma_debug_check
Chris@49:       (
Chris@49:       (P_is_vec == false) && (P.n_rows != P.n_cols),
Chris@49:       "diagmat(): only vectors and square matrices are accepted"
Chris@49:       );
Chris@49:     }
Chris@49:   
Chris@49:   inline ~diagmat_proxy_check()
Chris@49:     {
Chris@49:     if(P_local) { delete P_local; }
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P_is_vec ? P[i] : P.at(i,i);                                         }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? ( P_is_vec ? P[row] : P.at(row,row) ) : elem_type(0); }
Chris@49:   
Chris@49:   const Mat<eT>* P_local;
Chris@49:   const Mat<eT>& P;
Chris@49:   const bool     P_is_vec;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy_check< Row<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check(const Row<eT>& X, const Mat<eT>& out)
Chris@49:     : P_local ( (&X == reinterpret_cast<const Row<eT>*>(&out)) ? new Row<eT>(X) : 0 )
Chris@49:     , P       ( (&X == reinterpret_cast<const Row<eT>*>(&out)) ? (*P_local)     : X )
Chris@49:     , n_elem  (X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   inline ~diagmat_proxy_check()
Chris@49:     {
Chris@49:     if(P_local) { delete P_local; }
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Row<eT>* P_local;
Chris@49:   const Row<eT>& P;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy_check< Col<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check(const Col<eT>& X, const Mat<eT>& out)
Chris@49:     : P_local ( (&X == reinterpret_cast<const Col<eT>*>(&out)) ? new Col<eT>(X) : 0 )
Chris@49:     , P       ( (&X == reinterpret_cast<const Col<eT>*>(&out)) ? (*P_local)     : X )
Chris@49:     , n_elem  (X.n_elem)
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   inline ~diagmat_proxy_check()
Chris@49:     {
Chris@49:     if(P_local) { delete P_local; }
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Col<eT>* P_local;
Chris@49:   const Col<eT>& P;
Chris@49:   const uword    n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy_check< subview_row<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check(const subview_row<eT>& X, const Mat<eT>&)
Chris@49:     : P       ( X )
Chris@49:     , n_elem  ( X.n_elem )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Row<eT> P;
Chris@49:   const uword   n_elem;
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: template<typename eT>
Chris@49: class diagmat_proxy_check< subview_col<eT> >
Chris@49:   {
Chris@49:   public:
Chris@49:   
Chris@49:   typedef          eT                              elem_type;
Chris@49:   typedef typename get_pod_type<elem_type>::result pod_type;
Chris@49:   
Chris@49:   inline
Chris@49:   diagmat_proxy_check(const subview_col<eT>& X, const Mat<eT>& out)
Chris@49:     : P     ( const_cast<eT*>(X.colptr(0)), X.n_rows, (&(X.m) == &out), false )
Chris@49:     , n_elem( X.n_elem )
Chris@49:     //, X_ref ( X )
Chris@49:     {
Chris@49:     arma_extra_debug_sigprint();
Chris@49:     }
Chris@49:   
Chris@49:   arma_inline elem_type operator[] (const uword i)                    const { return P[i];                                 }
Chris@49:   arma_inline elem_type at         (const uword row, const uword col) const { return (row == col) ? P[row] : elem_type(0); }
Chris@49:   
Chris@49:   static const bool P_is_vec = true;
Chris@49:   
Chris@49:   const Col<eT> P;
Chris@49:   const uword   n_elem;
Chris@49:   
Chris@49:   //const subview_col<eT>& X_ref;   // prevents the compiler from potentially deleting X before we're done with it
Chris@49:   };
Chris@49: 
Chris@49: 
Chris@49: 
Chris@49: //! @}