diff --git a/src/include/operation/op_types.cc.h b/src/include/operation/op_types.cc.h
index f09cd97..800855b 100644
--- a/src/include/operation/op_types.cc.h
+++ b/src/include/operation/op_types.cc.h
@@ -4,7 +4,7 @@
 
 #include "op_types.h"
 //#include "xpr/xpr.h"
-//#include "op_utility.h"
+#include "op_utility.h"
 #include "extensions/extensions.h"
 
 namespace CNORXZ
@@ -33,7 +33,7 @@ namespace CNORXZ
     template <class F, class... Args>
     constexpr decltype(auto) COpInterface<OpT>::o(F&& f, Args&&... args) const
     {
-	return mkOperation(std::forward<F>(f), THIS().r(), args...);
+	return operation(std::forward<F>(f), THIS().r(), args...);
     }
 
     
@@ -45,7 +45,7 @@ namespace CNORXZ
     template <class IndexT, class F, class... Args>
     constexpr decltype(auto) OpInterface<OpT>::ax(const Sptr<IndexT>& ind, F&& f, const Args&... args)
     {
-	return ind->ifor( mkOperation(f, OI::THIS().r(), args...), NoF {} );
+	return ind->ifor( operation(f, OI::THIS().r(), args...), NoF {} );
     }
 
     template <class OpT>
@@ -116,7 +116,13 @@ namespace CNORXZ
     {
 	return COpRoot<T,IndexT>(a, ind);
     }
-    
+
+    template <typename T, class IndexT>
+    constexpr decltype(auto) coproot(const T* a, const Sptr<IndexT>& ind)
+    {
+	return COpRoot<T,IndexT>(a, ind);
+    }
+
     /****************
      *   OpCont     *
      ****************/
@@ -364,7 +370,7 @@ namespace CNORXZ
     }
 
     template <class F, class... Ops>
-    constexpr decltype(auto) mkOperation(F&& f, const Ops&... ops)
+    constexpr decltype(auto) operation(F&& f, const Ops&... ops)
     {
 	return Operation<F,Ops...>(std::forward<F>(f), ops...);
     }
@@ -400,11 +406,21 @@ namespace CNORXZ
     }
 
     template <class F, class Op, class IndexT>
-    constexpr decltype(auto) mkContracion(F&& f, Op&& op, const Sptr<IndexT>& i)
+    constexpr decltype(auto) contracion(F&& f, Op&& op, const Sptr<IndexT>& i)
     {
 	typedef decltype(i->ifor( op, f )) CXprT; // TODO: implement ifor with func arg!!!
 	return Contraction<CXprT>( i->ifor( op, f ) );
     }
+
+    /************************
+     *   various functions  *
+     ************************/
+    
+    template <class IndexT>
+    constexpr decltype(auto) indexOp(const Sptr<IndexT>& i)
+    {
+	return i->xpr(i);
+    }
 }
 
 #endif
diff --git a/src/include/operation/op_types.h b/src/include/operation/op_types.h
index 0624425..827f4ad 100644
--- a/src/include/operation/op_types.h
+++ b/src/include/operation/op_types.h
@@ -93,7 +93,10 @@ namespace CNORXZ
 
     template <typename T, class IndexT>
     constexpr decltype(auto) coproot(const CArrayBase<T>& a, const Sptr<IndexT>& ind);
-    
+
+    template <typename T, class IndexT>
+    constexpr decltype(auto) coproot(const T* a, const Sptr<IndexT>& ind);
+
     template <typename T, class IndexT>
     class OpCont : public OpInterface<OpCont<T,IndexT>>
     {
@@ -207,7 +210,7 @@ namespace CNORXZ
     };
 
     template <class F, class... Ops>
-    constexpr decltype(auto) mkOperation(F&& f, const Ops&... ops);
+    constexpr decltype(auto) operation(F&& f, const Ops&... ops);
 
     template <class F, class... Ops>
     struct op_size<Operation<F,Ops...>>
@@ -236,7 +239,10 @@ namespace CNORXZ
     };
 
     template <class F, class Op, class IndexT>
-    constexpr decltype(auto) mkContracion(F&& f, Op&& op, const Sptr<IndexT>& i);
+    constexpr decltype(auto) contracion(F&& f, Op&& op, const Sptr<IndexT>& i);
+
+    template <class IndexT>
+    constexpr decltype(auto) indexOp(const Sptr<IndexT>& i);
 }
 
 #endif
diff --git a/src/include/operation/op_utility.cc.h b/src/include/operation/op_utility.cc.h
index fa4462e..ed8fa45 100644
--- a/src/include/operation/op_utility.cc.h
+++ b/src/include/operation/op_utility.cc.h
@@ -33,20 +33,20 @@ namespace CNORXZ
     }
 
     template <class F, class PosT, class OpTuple, class OpSizes, SizeT... Is>
-    inline void pos_unpack_args_i(const F& f, const PosT& pos, const OpTuple& args,
+    inline auto pos_unpack_args_i(const F& f, const PosT& pos, const OpTuple& args,
 				  OpSizes opsizes, std::index_sequence<Is...> is)
     {
-	f(std::get<Is>(args)(pos_get<sum_index_sequence<Is>(opsizes)>(pos))...);
+	return f(std::get<Is>(args)(pos_get<sum_index_sequence<Is>(opsizes)>(pos))...);
     }
 
     template <class F, class PosT, class... Ops>
-    inline void pos_unpack_args(const F& f, const PosT& pos, const Tuple<Ops...>& args)
+    inline auto pos_unpack_args(const F& f, const PosT& pos, const Tuple<Ops...>& args)
     {
 	static_assert(is_pos_type<PosT>::value, "got non-pos-type");
 	static_assert((is_operation<Ops>::value and ...), "got non-operation type");
 	typedef std::make_index_sequence<sizeof...(Ops)> Idxs;
 	typedef std::index_sequence<op_size<Ops>::value...> OpSizes;
-	pos_unpack_args_i(f, pos, args, OpSizes{}, Idxs{});
+	return pos_unpack_args_i(f, pos, args, OpSizes{}, Idxs{});
     }
 
 }
diff --git a/src/include/operation/op_utility.h b/src/include/operation/op_utility.h
index 05be1a0..dfabab4 100644
--- a/src/include/operation/op_utility.h
+++ b/src/include/operation/op_utility.h
@@ -13,11 +13,11 @@ namespace CNORXZ
     constexpr SizeT sum_index_sequence(std::index_sequence<Is...> is);
 
     template <class F, class PosT, class OpTuple, class OpSizes, SizeT... Is>
-    inline void pos_unpack_args_i(const F& f, const PosT& pos, const OpTuple& args,
+    inline auto pos_unpack_args_i(const F& f, const PosT& pos, const OpTuple& args,
 				  OpSizes opsizes, std::index_sequence<Is...> is);
     
     template <class F, class PosT, class... Ops>
-    inline void pos_unpack_args(const F& f, const PosT& pos, const Tuple<Ops...>& args);
+    inline auto pos_unpack_args(const F& f, const PosT& pos, const Tuple<Ops...>& args);
     
 }
 
diff --git a/src/include/ranges/crange.h b/src/include/ranges/crange.h
index 549bca6..0f5e7a8 100644
--- a/src/include/ranges/crange.h
+++ b/src/include/ranges/crange.h
@@ -41,6 +41,7 @@ namespace CNORXZ
 	String stringMeta() const;
 	SizeT meta() const;
 	CIndex& at(const SizeT& metaPos);
+	COpRoot<SizeT,CIndex> xpr(const Sptr<CIndex>& _this) const;
 
 	template <class Index>
 	decltype(auto) format(const Sptr<Index>& ind) const;
diff --git a/src/include/ranges/dindex.h b/src/include/ranges/dindex.h
index 2a0df57..f5cbfde 100644
--- a/src/include/ranges/dindex.h
+++ b/src/include/ranges/dindex.h
@@ -53,7 +53,8 @@ namespace CNORXZ
 	String stringMeta() const;
 	DType meta() const;
 	DIndex& at(const DType& meta);
-
+	DXpr<SizeT> xpr(const Sptr<DIndex>& _this) const;
+	
 	DXpr<SizeT> ifor(const DXpr<SizeT>& xpr, std::function<SizeT(SizeT,SizeT)>&& f) const;
 
 	const XIndexPtr& xptr() const;
diff --git a/src/include/ranges/index_base.h b/src/include/ranges/index_base.h
index d2925ef..74e6f7a 100644
--- a/src/include/ranges/index_base.h
+++ b/src/include/ranges/index_base.h
@@ -53,6 +53,7 @@ namespace CNORXZ
 	String stringMeta() const { return THIS().stringMeta(); }
 	decltype(auto) meta() const { return THIS().meta(); }
 	I& at(const MetaType& meta) { return THIS().at(meta); }
+	decltype(auto) xpr(const Sptr<I>& _this) const { return THIS().xpr(_this); }
 
 	//template <class Index>
 	//decltype(auto) format(const Sptr<Index>& ind) const { return THIS().format(ind); }
diff --git a/src/include/ranges/mrange.cc.h b/src/include/ranges/mrange.cc.h
index 32225f3..980ec22 100644
--- a/src/include/ranges/mrange.cc.h
+++ b/src/include/ranges/mrange.cc.h
@@ -3,6 +3,9 @@
 #define __cxz_mrange_cc_h__
 
 #include "mrange.h"
+#include "operation/op_types.h"
+#include "operation/op_types.cc.h" // -> do .cc files
+#include "operation/op_utility.cc.h" // -> do .cc files
 
 namespace CNORXZ
 {
@@ -408,6 +411,17 @@ namespace CNORXZ
 	      [](const auto&... xs) { return (xs + ...); });
 	return *this;
     }
+
+    template <class FormatT, class... Indices>	
+    decltype(auto) GMIndex<FormatT,Indices...>::xpr(const Sptr<MIndex<Indices...>>& _this) const
+    {
+	return iter<0,NI>( [&](auto i) { return _this->pack()[i]->xpr( _this->pack()[i] ); },
+			   [](const auto&... x) {
+			       return operation( [](const auto&... e) {
+				   return std::make_tuple(e...);
+			       }, x... );
+			   } );
+    }
     
     template <class FormatT, class... Indices>	
     template <class Xpr, class F>
diff --git a/src/include/ranges/mrange.h b/src/include/ranges/mrange.h
index dd80c28..f9a950c 100644
--- a/src/include/ranges/mrange.h
+++ b/src/include/ranges/mrange.h
@@ -65,6 +65,7 @@ namespace CNORXZ
 	String stringMeta() const;
 	MetaType meta() const;
 	GMIndex& at(const MetaType& metaPos);
+	decltype(auto) xpr(const Sptr<MIndex<Indices...>>& _this) const;
 	
 	template <class Xpr, class F>
 	constexpr decltype(auto) ifor(const Xpr& xpr, F&& f) const;
diff --git a/src/include/ranges/urange.cc.h b/src/include/ranges/urange.cc.h
index f9d51e8..db64eec 100644
--- a/src/include/ranges/urange.cc.h
+++ b/src/include/ranges/urange.cc.h
@@ -8,6 +8,8 @@
 #include "urange.h"
 #include "index_mul.h"
 #include "xpr/for.h"
+#include "operation/op_types.h"
+#include "operation/op_types.cc.h"
 
 namespace CNORXZ
 {
@@ -118,6 +120,12 @@ namespace CNORXZ
 	return *this;
     }
 
+    template <typename MetaType>
+    decltype(auto) UIndex<MetaType>::xpr(const Sptr<UIndex<MetaType>>& _this) const
+    {
+	return coproot(mMetaPtr,_this);
+    }
+
     template <typename MetaType>
     size_t UIndex<MetaType>::dim() const // = 1
     {
diff --git a/src/include/ranges/urange.h b/src/include/ranges/urange.h
index 39e5471..5fdbcf2 100644
--- a/src/include/ranges/urange.h
+++ b/src/include/ranges/urange.h
@@ -46,6 +46,7 @@ namespace CNORXZ
 	String stringMeta() const;
 	const MetaT& meta() const;
 	UIndex& at(const MetaT& metaPos);
+	decltype(auto) xpr(const Sptr<UIndex<MetaType>>& _this) const;
 
 	template <class Index>
 	decltype(auto) format(const Sptr<Index>& ind) const;
diff --git a/src/include/ranges/xindex.cc.h b/src/include/ranges/xindex.cc.h
index 589c3ec..6fd6601 100644
--- a/src/include/ranges/xindex.cc.h
+++ b/src/include/ranges/xindex.cc.h
@@ -209,6 +209,13 @@ namespace CNORXZ
 	return *this;
     }
 
+    template <class Index, typename Meta>
+    DXpr<SizeT> XIndex<Index,Meta>::xpr(const XIndexPtr& _this) const
+    {
+	auto xthis = std::dynamic_pointer_cast<Index>(_this);
+	return DXpr<SizeT>( mI->xpr(xthis) );
+    }
+
     template <class Index, typename Meta>
     DXpr<SizeT> XIndex<Index,Meta>::ifor(const DXpr<SizeT>& xpr,
 					 std::function<SizeT(SizeT,SizeT)>&& f) const
diff --git a/src/include/ranges/xindex.h b/src/include/ranges/xindex.h
index 02eca13..9940b4a 100644
--- a/src/include/ranges/xindex.h
+++ b/src/include/ranges/xindex.h
@@ -45,6 +45,7 @@ namespace CNORXZ
 	virtual String stringMeta() const = 0;
 	virtual DType meta() const = 0;
 	virtual XIndexBase& at(const DType& meta) = 0;
+	virtual DXpr<SizeT> xpr(const XIndexPtr& _this) const = 0;
 
 	virtual DXpr<SizeT> ifor(const DXpr<SizeT>& xpr,
 				 std::function<SizeT(SizeT,SizeT)>&& f) const = 0;
@@ -97,6 +98,7 @@ namespace CNORXZ
 	virtual String stringMeta() const override final;
 	virtual DType meta() const override final;
 	virtual XIndexBase& at(const DType& meta) override final;
+	virtual DXpr<SizeT> xpr(const XIndexPtr& _this) const override final;
 
 	virtual DXpr<SizeT> ifor(const DXpr<SizeT>& xpr,
 				 std::function<SizeT(SizeT,SizeT)>&& f) const override final;
diff --git a/src/include/ranges/yrange.h b/src/include/ranges/yrange.h
index 14d4f4b..43f6f8b 100644
--- a/src/include/ranges/yrange.h
+++ b/src/include/ranges/yrange.h
@@ -53,6 +53,7 @@ namespace CNORXZ
 	String stringMeta() const;
 	Vector<DType> meta() const;
 	YIndex& at(const Vector<DType>& meta);
+	DXpr<SizeT> xpr(const Sptr<YIndex>& _this) const;
 
 	DXpr<SizeT> ifor(const DXpr<SizeT>& xpr, std::function<SizeT(SizeT,SizeT)>&& f) const;
 
diff --git a/src/include/xpr/xpr_base.cc.h b/src/include/xpr/xpr_base.cc.h
index dcc24c5..71421c8 100644
--- a/src/include/xpr/xpr_base.cc.h
+++ b/src/include/xpr/xpr_base.cc.h
@@ -25,13 +25,17 @@ namespace CNORXZ
     template <typename T, class Xpr>
     T VXpr<T,Xpr>::vexec(const DPos& last) const
     {
-	return (*this)(last);
+	CXZ_ERROR("IMPLEMENT!!!" << last.val());
+	//(*this)(last);
+	return T();
     }
 
     template <typename T, class Xpr>
     T VXpr<T,Xpr>::vexec() const
     {
-	return (*this)();
+	CXZ_ERROR("IMPLEMENT!!!");
+	//(*this)();
+	return T();
     }
     
     template <typename T, class Xpr>
diff --git a/src/lib/ranges/crange.cc b/src/lib/ranges/crange.cc
index 2d4182d..0e44f03 100644
--- a/src/lib/ranges/crange.cc
+++ b/src/lib/ranges/crange.cc
@@ -1,5 +1,6 @@
 
 #include "ranges/ranges.h"
+#include "operation/operation.h"
 
 namespace CNORXZ
 {
@@ -106,6 +107,19 @@ namespace CNORXZ
 	IB::mPos = metaPos;
 	return *this;
     }
+
+    COpRoot<SizeT,CIndex> CIndex::xpr(const Sptr<CIndex>& _this) const
+    {
+	// preliminary solution (TODO: implement xpr that simply returns PosT value):
+	static Vector<SizeT> m;
+	if(m.size() < _this->lmax().val()){
+	    m.resize(_this->lmax().val());
+	    for(SizeT i = 0; i != m.size(); ++i) {
+		m[i] = i;
+	    }
+	}
+	return coproot(m.data(), _this);
+    }
     
     
     /**********************
diff --git a/src/lib/ranges/dindex.cc b/src/lib/ranges/dindex.cc
index 4af6bfb..3c420c1 100644
--- a/src/lib/ranges/dindex.cc
+++ b/src/lib/ranges/dindex.cc
@@ -161,7 +161,12 @@ namespace CNORXZ
 	IB::mPos = mI->pos();
 	return *this;
     }
-    
+
+    DXpr<SizeT> DIndex::xpr(const Sptr<DIndex>& _this) const
+    {
+	return mI->xpr(_this->xptr());
+    }
+
     DXpr<SizeT> DIndex::ifor(const DXpr<SizeT>& xpr, std::function<SizeT(SizeT,SizeT)>&& f) const
     {
 	return DXpr<SizeT>(mI->ifor(xpr, std::forward<std::function<SizeT(SizeT,SizeT)>>(f)) );
diff --git a/src/lib/ranges/yrange.cc b/src/lib/ranges/yrange.cc
index 25eeec8..634d9fe 100644
--- a/src/lib/ranges/yrange.cc
+++ b/src/lib/ranges/yrange.cc
@@ -338,6 +338,12 @@ namespace CNORXZ
 	return *this;
     }
 
+    DXpr<SizeT> YIndex::xpr(const Sptr<YIndex>& _this) const
+    {
+	CXZ_ERROR("IMPLEMENT!!!" << _this->lmax().val());
+	return DXpr<SizeT>();
+    }
+
     DXpr<SizeT> YIndex::ifor(const DXpr<SizeT>& xpr, std::function<SizeT(SizeT,SizeT)>&& f) const
     {
 	return mkIFor(0, xpr, std::forward<std::function<SizeT(SizeT,SizeT)>>(f));
diff --git a/src/opt/hdf5/include/h5_content_base.h b/src/opt/hdf5/include/h5_content_base.h
index 3685936..ce77097 100644
--- a/src/opt/hdf5/include/h5_content_base.h
+++ b/src/opt/hdf5/include/h5_content_base.h
@@ -28,7 +28,6 @@ namespace CNORXZ
 	    virtual ContentType type() const = 0;
 	    virtual bool ro() const = 0;
 	    virtual ContentBase& open() = 0;
-	    virtual ContentBase& write() = 0;
 	    virtual ContentBase& close() = 0;
 	    virtual String path() const = 0;
 	    virtual String filename() const = 0;
diff --git a/src/opt/hdf5/include/h5_file.h b/src/opt/hdf5/include/h5_file.h
index 5c0a5f7..52c2849 100644
--- a/src/opt/hdf5/include/h5_file.h
+++ b/src/opt/hdf5/include/h5_file.h
@@ -23,7 +23,6 @@ namespace CNORXZ
 	    virtual ContentType type() const override final;
 	    virtual bool ro() const override final;
 	    virtual File& open() override final;
-	    virtual File& write() override final;
 	    virtual File& close() override final;
 	    virtual String path() const override final;
 	    virtual String filename() const override final;
diff --git a/src/opt/hdf5/include/h5_group.h b/src/opt/hdf5/include/h5_group.h
index da870c5..0196028 100644
--- a/src/opt/hdf5/include/h5_group.h
+++ b/src/opt/hdf5/include/h5_group.h
@@ -18,7 +18,6 @@ namespace CNORXZ
 	    virtual ContentType type() const override;
 	    virtual bool ro() const override;
 	    virtual Group& open() override; // load group if existing, else create new group
-	    virtual Group& write() override;
 	    virtual Group& close() override;
 	    virtual String path() const override;
 	    virtual String filename() const override;
diff --git a/src/opt/hdf5/include/h5_table.h b/src/opt/hdf5/include/h5_table.h
new file mode 100644
index 0000000..c1feb64
--- /dev/null
+++ b/src/opt/hdf5/include/h5_table.h
@@ -0,0 +1,38 @@
+
+#ifndef __cxz_h5_table_h__
+#define __cxz_h5_table_h__
+
+#include "h5_content_base.h"
+
+namespace CNORXZ
+{
+    namespace hdf5
+    {
+	class Table : public ContentBase
+	{
+	public:
+	    DEFAULT_MEMBERS(Table);
+	    Table(const String& name, const ContentBase* _parent);
+	    ~Table();
+
+	    virtual ContentType type() const override final;
+	    virtual bool ro() const override final;
+	    virtual Table& open() override final;
+	    virtual Table& close() override final;
+	    virtual String path() const override final;
+	    virtual String filename() const override final;
+	    
+	    template <class F>
+	    decltype(auto) readRecords(F&& f) const;
+	    
+	private:
+	    RangePtr mRecords;
+	    RangePtr mFields; // -> FIndex (position -> offset)
+	    MArray mSizes;
+	    MArray mOffsets;
+	    MArray mTypes;
+	};
+    }
+}
+
+#endif
diff --git a/src/opt/hdf5/lib/h5_file.cc b/src/opt/hdf5/lib/h5_file.cc
index 96fffd3..ec1452e 100644
--- a/src/opt/hdf5/lib/h5_file.cc
+++ b/src/opt/hdf5/lib/h5_file.cc
@@ -49,15 +49,6 @@ namespace CNORXZ
 	    return *this;
 	}
 	
-	File& File::write()
-	{
-	    CXZ_ASSERT( not mRo, "could not write to file: opened as read-only" );
-	    for(auto& x: mCont){
-		x->write();
-	    }
-	    return *this;
-	}
-	
 	File& File::close()
 	{
 	    if(mCont.range() != nullptr){
diff --git a/src/opt/hdf5/lib/h5_group.cc b/src/opt/hdf5/lib/h5_group.cc
index 28de33c..c909808 100644
--- a/src/opt/hdf5/lib/h5_group.cc
+++ b/src/opt/hdf5/lib/h5_group.cc
@@ -40,12 +40,6 @@ namespace CNORXZ
 	    return *this;
 	}
 	
-	Group& Group::write()
-	{
-	    // ...!!!
-	    return *this;
-	}
-
 	Group& Group::close()
 	{
 	    if(mId != 0){