diff --git a/src/include/array/array_base.cc.h b/src/include/array/array_base.cc.h
index 80ce363..02daf86 100644
--- a/src/include/array/array_base.cc.h
+++ b/src/include/array/array_base.cc.h
@@ -18,9 +18,9 @@
 
 namespace CNORXZ
 {
-    /******************
-     *   CArrayBase   *
-     ******************/
+    /*=======================================================+
+     |    Implementations for CArrayBase member functions    |
+     +=======================================================*/
 
     template <typename T>
     CArrayBase<T>::CArrayBase(const RangePtr& range) :
@@ -31,6 +31,11 @@ namespace CNORXZ
     template <typename I, typename M>
     const T& CArrayBase<T>::operator[](const IndexInterface<I,M>& i) const
     {
+	/*
+	  TODO: check if container format is trivial:
+	  if yes, just return data[i.lex()], in case of at() check extensions
+	  if not, do what is done now
+	 */
 	auto ai = itLex(i);
 	return *ai;
     }
@@ -111,6 +116,13 @@ namespace CNORXZ
     template <class Index>
     COpRoot<T,Index> CArrayBase<T>::operator()(const Sptr<Index>& i) const
     {
+	/*
+	  TODO: check if container format is trivial
+	  if yes, assert that index format is trivial and has correct extensions
+	  if not, check if index format is trivial
+	  - if yes: try to apply container format
+	  - if not: check if format is compatible
+	 */
 	this->checkFormatCompatibility(*i);
 	return coproot(*this, i);
     }
@@ -132,9 +144,9 @@ namespace CNORXZ
 	return coproot(*this, i);
     }
 
-    /******************************
-     *   CArrayBase (protected)   *
-     ******************************/
+    /*=================================================================+
+     |    Implementations for protected CArrayBase member functions    |
+     +=================================================================*/
 
     template <typename T>
     template <class Acc>
@@ -185,9 +197,9 @@ namespace CNORXZ
 	}
     }
 
-    /*****************
-     *   ArrayBase   *
-     *****************/
+    /*======================================================+
+     |    Implementations for ArrayBase member functions    |
+     +======================================================*/
 
     template <typename T>
     ArrayBase<T>::ArrayBase(const RangePtr& range) :
@@ -287,9 +299,9 @@ namespace CNORXZ
 	return oproot(*this, i);
     }
 
-    /*****************************
-     *   ArrayBase (protected)   *
-     *****************************/
+    /*================================================================+
+     |    Implementations for protected ArrayBase member functions    |
+     +================================================================*/
 
     template <typename T>
     template <class Acc>
diff --git a/src/include/array/array_base.h b/src/include/array/array_base.h
index 9d67752..155325a 100644
--- a/src/include/array/array_base.h
+++ b/src/include/array/array_base.h
@@ -24,75 +24,175 @@
 
 namespace CNORXZ
 {
+    /** ****
+	Abstract container base class
+	only read access to the data
+	
+	@tparam T data type
+     */
     template <typename T>
     class CArrayBase
     {
     public:
-	typedef AIndex<T> const_iterator;
+	typedef AIndex<T> const_iterator; /** const iterator type */
 
+	DEFAULT_MEMBERS(CArrayBase); /**< default constructors and assignments */
+
+	/** construct container on a range
+	    @param range 
+	 */
 	CArrayBase(const RangePtr& range);
-	DEFAULT_MEMBERS(CArrayBase);
 
+	/** default destructor */
 	virtual ~CArrayBase() = default;
 
+	/** const data element access
+	    @tparam I index type
+	    @tparam M meta data type
+	    @param i index
+	 */
 	template <typename I, typename M>
 	const T& operator[](const IndexInterface<I,M>& i) const;
 
+	/** const data element access
+	    performs compatibility checks 
+	    @tparam I index type
+	    @tparam M meta data type
+	    @param i index
+	 */
 	template <typename I, typename M>
 	const T& at(const IndexInterface<I,M>& i) const;
 
+	/** const data element access
+	    @tparam I index type
+	    @tparam M meta data type
+	    @param pack static index pack
+	 */
 	template <class... Indices>
 	const T& operator[](const SPack<Indices...>& pack) const;
 
+	/** const data element access
+	    performs compatibility checks 
+	    @tparam I index type
+	    @tparam M meta data type
+	    @param i static index pack
+	 */
 	template <class... Indices>
 	const T& at(const SPack<Indices...>& pack) const;
 
+	/** const data element access
+	    @param pack index pack
+	 */
 	const T& operator[](const DPack& pack) const;
+
+	/** const data element access
+	    performs compatibility checks 
+	    @param i index pack
+	 */
 	const T& at(const DPack& pack) const;
 
+	/** create hypercubic slice from this container
+	    @tparam I type of index used to indicate slice edges
+	    @tparam M index meta type
+	    @param begin begin edge
+	    @param end end edge
+	 */
 	template <typename I, typename M>
 	Sptr<CArrayBase<T>> sl(const IndexInterface<I,M>& begin,
 			       const IndexInterface<I,M>& end) const;
 
+	/** create operation on this container
+	    @tparam Index type of operation index
+	    @param i operation index
+	 */
 	template <class Index>
 	COpRoot<T,Index> operator()(const Sptr<Index>& i) const;
 
+	/** create operation on this container
+	    @tparam Indices types of operation indices
+	    @param pack pack of operation index
+	 */
 	template <class... Indices>
 	inline decltype(auto) operator()(const SPack<Indices...>& pack) const;
 
+	/** create operation on this container
+	    @param pack pack of operation index
+	 */
 	inline decltype(auto) operator()(const DPack& pack) const;
 
+	/** get pointer to container data */
 	virtual const T* data() const = 0;
+
+	/** get number of elements in the container */
 	virtual SizeT size() const;
+
+	/** get container range */
 	virtual RangePtr range() const;
 
+	/** get index pointing to first position */
 	virtual const_iterator begin() const;
+
+	/** get index pointing to position after last position */
 	virtual const_iterator end() const;
+
+	/** get index pointing to first position */
 	virtual const_iterator cbegin() const = 0;
+
+	/** get index pointing to position after last position */
 	virtual const_iterator cend() const = 0;
 
+	/** check if container views the data, i.e. it does not own it */
 	virtual bool isView() const = 0;
 
     protected:
-	RangePtr mRange;
+	RangePtr mRange; /**< the container range */
 
+	/** Get valid data index.
+	    Create well-formated index from index pack (unformatted)
+	    or index using trivial format.
+	    @tparam Acc index type or index pack type
+	    @param acc index or index pack
+	 */
 	template <class Acc>
 	const_iterator itLex(const Acc& acc) const;
 
+	/** Get valid data index.
+	    Create well-formated index from index pack (unformatted)
+	    or index using trivial format.
+	    Perform compatibility checks.
+	    @tparam Acc index type or index pack type
+	    @param acc index or index pack
+	 */
 	template <class Acc>
 	const_iterator itLexSave(const Acc& acc) const;
 
+	/** Perform compatibility checks
+	    @tparam Acc index type or index pack type
+	    @param acc index or index pack.
+	 */
 	template <class Acc>
 	void checkFormatCompatibility(const Acc& acc) const;
+
+	/** check if format is trivial
+	    @return true is container is data owning array, else return
+	    result of the corresponding container index
+	 */
+	virtual bool formatIsTrivial() const = 0;
     };
 
+    /** ****
+	Abstract container base class
+	read and write access to the data
+
+	@tparam T data type
+     */
     template <typename T>
     class ArrayBase : public CArrayBase<T>
     {
     public:
 	typedef CArrayBase<T> CAB;
-	typedef typename CAB::const_iterator const_iterator;
-	typedef BIndex<T> iterator;
+	typedef typename CAB::const_iterator const_iterator; /**< constant iterator type */
+	typedef BIndex<T> iterator; /**< read/write iterator type */
 
 	using CAB::operator[];
 	using CAB::operator();
@@ -103,48 +203,85 @@ namespace CNORXZ
 	using CAB::cbegin;
 	using CAB::cend;
 	using CAB::sl;
-	//using CAB::operator();
 
+	DEFAULT_MEMBERS(ArrayBase); /**< default constructors and assignments */
+
+	/** construct a container on a range
+	 */
 	ArrayBase(const RangePtr& range);
-	DEFAULT_MEMBERS(ArrayBase);
 
+	/** @copydoc CArrayBase::operator[]()
+	 */
 	template <typename I, typename M>
 	T& operator[](const IndexInterface<I,M>& i);
 
+	/** @copydoc CArrayBase::at()
+	 */
 	template <typename I, typename M>
 	T& at(const IndexInterface<I,M>& i);
 
+	/** @copydoc CArrayBase::operator[]()
+	 */
 	template <class... Indices>
 	T& operator[](const SPack<Indices...>& pack);
 
+	/** @copydoc CArrayBase::at()
+	 */
 	template <class... Indices>
 	T& at(const SPack<Indices...>& pack);
 
+	/** @copydoc CArrayBase::operator[]()
+	 */
 	T& operator[](const DPack& pack);
+
+	/** @copydoc CArrayBase::at()
+	 */
 	T& at(const DPack& pack);
 
+	/** @copydoc CArrayBase::operator()()
+	 */
 	template <class Index>
 	OpRoot<T,Index> operator()(const Sptr<Index>& i);
 
+	/** @copydoc CArrayBase::operator()()
+	 */
 	template <class... Indices>
 	inline decltype(auto) operator()(const SPack<Indices...>& pack);
 
+	/** @copydoc CArrayBase::operator()()
+	 */
 	inline decltype(auto) operator()(const DPack& pack);
 
+	/** @copydoc CArrayBase::sl()
+	 */
 	template <typename I, typename M>
 	Sptr<ArrayBase<T>> sl(const IndexInterface<I,M>& begin,
 			      const IndexInterface<I,M>& end);
 
+	/** @copydoc CArrayBase::data()
+	    read/write access
+	 */
 	virtual T* data() = 0;
 	
+	/** @copydoc CArrayBase::begin()
+	    read/write access
+	 */
 	virtual iterator begin();
+
+	/** @copydoc CArrayBase::end()
+	    read/write access
+	 */
 	virtual iterator end();
 	
     protected:
 	
+	/** @copydoc CArrayBase::itLex()
+	 */
 	template <class Acc>
 	iterator itLex(const Acc& acc);
 
+	/** @copydoc CArrayBase::itLexSave()
+	 */
 	template <class Acc>
 	iterator itLexSave(const Acc& acc);
     };
diff --git a/src/include/array/marray.cc.h b/src/include/array/marray.cc.h
index 591ce8e..3ea3923 100644
--- a/src/include/array/marray.cc.h
+++ b/src/include/array/marray.cc.h
@@ -17,9 +17,9 @@
 
 namespace CNORXZ
 {
-    /****************
-     *    MArray    *
-     ***************/
+    /*=======================================================+
+     |    Implementation of MArray public member functions   |
+     +=======================================================*/
     
     template <typename T>
     MArray<T>::MArray(const RangePtr& range) :
@@ -92,6 +92,15 @@ namespace CNORXZ
 	return false;
     }
     
+    /*==========================================================+
+     |    Implementation of MArray protected member functions   |
+     +==========================================================*/
+
+    template <typename T>
+    bool MArray<T>::formatIsTrivial() const
+    {
+	return true;
+    }
 }
 
 #endif
diff --git a/src/include/array/marray.h b/src/include/array/marray.h
index 1f561ea..8195e16 100644
--- a/src/include/array/marray.h
+++ b/src/include/array/marray.h
@@ -42,6 +42,9 @@ namespace CNORXZ
 	virtual bool isView() const override;
 
 	SERIALIZATION_FUNCTIONS;
+
+    protected:
+	virtual bool formatIsTrivial() const override final;
 	
     private:
 	Vector<T> mCont;
diff --git a/src/include/array/slice.cc.h b/src/include/array/slice.cc.h
index a1df1d0..1dca0cf 100644
--- a/src/include/array/slice.cc.h
+++ b/src/include/array/slice.cc.h
@@ -17,9 +17,9 @@
 
 namespace CNORXZ
 {
-    /**************
-     *   CSlice   *
-     **************/
+    /*========================================================+
+     |    Implementation of public CSlice member functions    |
+     +========================================================*/
     
     template <typename T>
     CSlice<T>::CSlice(const RangePtr& range, const CArrayBase<T>* parent,
@@ -54,9 +54,19 @@ namespace CNORXZ
 	return true;
     }
 
-    /*************
-     *   Slice   *
-     *************/
+    /*===========================================================+
+     |    Implementation of protected CSlice member functions    |
+     +===========================================================*/
+
+    template <typename T>
+    bool CSlice<T>::formatIsTrivial() const
+    {
+	return cbegin().formatIsTrivial();
+    }
+
+    /*=======================================================+
+     |    Implementation of public Slice member functions    |
+     +=======================================================*/
 
     template <typename T>
     Slice<T>::Slice(const RangePtr& range, ArrayBase<T>* parent,
@@ -96,6 +106,16 @@ namespace CNORXZ
     {
 	return true;
     }
+
+    /*==========================================================+
+     |    Implementation of protected Slice member functions    |
+     +==========================================================*/
+
+    template <typename T>
+    bool Slice<T>::formatIsTrivial() const
+    {
+	return cbegin().formatIsTrivial();
+    }
 }
 
 #endif
diff --git a/src/include/array/slice.h b/src/include/array/slice.h
index 9959dc8..a636b1a 100644
--- a/src/include/array/slice.h
+++ b/src/include/array/slice.h
@@ -18,6 +18,12 @@
 
 namespace CNORXZ
 {
+    /** ****
+	constant and possibly partial view on the data
+	of another container
+
+	@tparam T data type
+     */
     template <typename T>
     class CSlice : public CArrayBase<T>
     {
@@ -25,13 +31,15 @@ namespace CNORXZ
 	typedef CArrayBase<T> AB;
 	typedef typename AB::const_iterator const_iterator;
 
-    protected:
-	const CArrayBase<T>* mCParent = nullptr;
-	YFormat mBlockSizes;
-	SizeT mOff = 0;
-	
-    public:
-	DEFAULT_MEMBERS(CSlice);
+	DEFAULT_MEMBERS(CSlice); /**< default constructors and assignments */
+
+	/** create slice from an array
+
+	    @param range the slice's container range
+	    @param parent the original container
+	    @param blockSizes the format of the slice
+	    @param off the initial pointer position w.r.t. the original initial position
+	 */
 	CSlice(const RangePtr& range, const CArrayBase<T>* parent,
 	       const YFormat& blockSizes, SizeT off);
 	
@@ -39,23 +47,39 @@ namespace CNORXZ
 	virtual const_iterator cbegin() const override;
 	virtual const_iterator cend() const override;
 	virtual bool isView() const override final;
+
+    protected:
+
+	virtual bool formatIsTrivial() const override final;
+	
+	const CArrayBase<T>* mCParent = nullptr; /**< pointer to the original container */
+	YFormat mBlockSizes; /**< the format */
+	SizeT mOff = 0; /** pointer offset w.r.t. the original pointer */
+	
     };
 
+    /** ****
+	possibly partial view on the data
+	of another container
+
+	@tparam T data type
+     */
     template <typename T>
     class Slice : public ArrayBase<T>
     {
     public:
 	typedef CArrayBase<T> AB;
-	//typedef CSlice<T> CS;
 	typedef typename AB::const_iterator const_iterator;
 
-    private:
-	ArrayBase<T>* mParent = nullptr;
-	YFormat mBlockSizes;
-	SizeT mOff = 0;
+	DEFAULT_MEMBERS(Slice); /**< default constructors and assignments */
 
-    public:
-	DEFAULT_MEMBERS(Slice);
+	/** create slice from an array
+
+	    @param range the slice's container range
+	    @param parent the original container
+	    @param blockSizes the format of the slice
+	    @param off the initial pointer position w.r.t. the original initial position
+	 */
 	Slice(const RangePtr& range, ArrayBase<T>* parent,
 	      const YFormat& blockSizes, SizeT off);
 
@@ -64,6 +88,15 @@ namespace CNORXZ
 	virtual const_iterator cbegin() const override;
 	virtual const_iterator cend() const override;
 	virtual bool isView() const override final;
+
+    protected:
+	virtual bool formatIsTrivial() const override final;
+
+    private:
+	ArrayBase<T>* mParent = nullptr;
+	YFormat mBlockSizes;
+	SizeT mOff = 0;
+
     };
 }
 
diff --git a/src/include/ranges/crange.h b/src/include/ranges/crange.h
index 5675b3f..07f6352 100644
--- a/src/include/ranges/crange.h
+++ b/src/include/ranges/crange.h
@@ -111,6 +111,9 @@ namespace CNORXZ
 	template <class Xpr, class F = NoF>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const;
 
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+	
     private:
 	Sptr<RangeType> mRangePtr;
     };
diff --git a/src/include/ranges/dindex.h b/src/include/ranges/dindex.h
index dfe98ad..80fe024 100644
--- a/src/include/ranges/dindex.h
+++ b/src/include/ranges/dindex.h
@@ -73,6 +73,9 @@ namespace CNORXZ
 
 	const XIndexPtr& xptr() const;
 	
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	XIndexPtr mI;
     };
diff --git a/src/include/ranges/index_base.h b/src/include/ranges/index_base.h
index 71d8a92..a246e3f 100644
--- a/src/include/ranges/index_base.h
+++ b/src/include/ranges/index_base.h
@@ -189,12 +189,15 @@ namespace CNORXZ
 	template <class Xpr, class F = NoF>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const
 	{ return THIS().ifor(xpr,std::forward<F>(f)); }
+
+	/** check is format is trivial */
+	bool formatIsTrivial() const { return THIS().formatIsTrivial(); }
 	
     protected:
 	SizeT mPos = 0; /**< the memory position */
 	
     private:
-	friend I; // why not protected???!!!
+	friend I; // not protected; I should really be something that is derived from IndexInterface
 	
 	// NO DEFAULT CONSTRUCTORS/ASSIGNMENTS!
 	IndexInterface();
diff --git a/src/include/ranges/mrange.cc.h b/src/include/ranges/mrange.cc.h
index 84a5020..81aae28 100644
--- a/src/include/ranges/mrange.cc.h
+++ b/src/include/ranges/mrange.cc.h
@@ -448,6 +448,13 @@ namespace CNORXZ
 	return mkIFor<0>(xpr, std::forward<F>(f));
     }
 
+    template <class FormatT, class... Indices>
+    bool GMIndex<FormatT,Indices...>::formatIsTrivial() const
+    {
+	CXZ_ERROR("IMPLEMENT!!!");
+	return true;
+    }
+
     template <class FormatT, class... Indices>
     GMIndex<FormatT,Indices...>& GMIndex<FormatT,Indices...>::operator()(const Sptr<MIndex<Indices...>>& mi)
     {
diff --git a/src/include/ranges/mrange.h b/src/include/ranges/mrange.h
index f805ad1..aa30d7c 100644
--- a/src/include/ranges/mrange.h
+++ b/src/include/ranges/mrange.h
@@ -93,6 +93,9 @@ namespace CNORXZ
 	auto deepFormat() const;
 	GMIndex& setFormat(const FormatT& bs);
 
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	template <SizeT... Is>
 	static constexpr decltype(auto) mkLexFormat(const SPack<Indices...>& ipack, Isq<Is...> is);
diff --git a/src/include/ranges/prange.cc.h b/src/include/ranges/prange.cc.h
index fea55ab..f670991 100644
--- a/src/include/ranges/prange.cc.h
+++ b/src/include/ranges/prange.cc.h
@@ -195,25 +195,6 @@ namespace CNORXZ
 	return mOrig->xpr(mOrig);
     }
 
-    template <class IndexT>
-    template <class I>
-    decltype(auto) PIndex<IndexT>::reformat(const Sptr<I>& ind) const
-    {
-	return ind;
-    }
-
-    template <class IndexT>
-    template <class I>
-    decltype(auto) PIndex<IndexT>::slice(const Sptr<I>& ind) const
-    {
-	if(ind != nullptr){
-	    if(ind->dim() != 0){
-		return Sptr<PIndex<IndexT>>();
-	    }
-	}
-	return std::make_shared<PIndex<IndexT>>(*this);
-    }
-
     template <class IndexT>
     template <class Xpr, class F>
     decltype(auto) PIndex<IndexT>::ifor(const Xpr& xpr, F&& f) const
@@ -222,6 +203,12 @@ namespace CNORXZ
 			       mRangePtr->parts().data(), xpr, std::forward<F>(f));
     }
 
+    template <class IndexT>
+    bool PIndex<IndexT>::formatIsTrivial() const
+    {
+	return mOrig->formatIsTrivial();
+    }
+
     template <class IndexT>
     PIndex<IndexT>& PIndex<IndexT>::operator()()
     {
diff --git a/src/include/ranges/prange.h b/src/include/ranges/prange.h
index ac3c1c6..419212f 100644
--- a/src/include/ranges/prange.h
+++ b/src/include/ranges/prange.h
@@ -61,12 +61,6 @@ namespace CNORXZ
 	PIndex& at(const MetaType& metaPos);
 	decltype(auto) xpr(const Sptr<PIndex<IndexT>>& _this) const;
 
-	template <class I>
-	decltype(auto) reformat(const Sptr<I>& ind) const;
-
-	template <class I>
-	decltype(auto) slice(const Sptr<I>& ind) const;
-
 	template <class Xpr, class F>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const;
 
@@ -74,6 +68,9 @@ namespace CNORXZ
 	PIndex& operator()(const Sptr<IndexT>& i);
 	const Sptr<IndexT>& orig() const;
 	
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	Sptr<RangeType> mRangePtr;
 	Sptr<IndexT> mOrig;
diff --git a/src/include/ranges/srange.cc.h b/src/include/ranges/srange.cc.h
index 481223e..bffa17f 100644
--- a/src/include/ranges/srange.cc.h
+++ b/src/include/ranges/srange.cc.h
@@ -176,26 +176,7 @@ namespace CNORXZ
     {
 	return 1;
     }
-    /*
-    template <typename MetaT, SizeT S>
-    template <class Index>
-    decltype(auto) SIndex<MetaT,S>::formatFrom(const Index& ind) const
-    {
-	return *this;
-    }
 
-    template <typename MetaT, SizeT S>
-    template <class Index>
-    decltype(auto) SIndex<MetaT,S>::slice(const Sptr<Index>& ind) const
-    {
-	if(ind != nullptr){
-	    if(ind->dim() != 0) {
-		return Sptr<SIndex<MetaType,S>>();
-	    }
-	}
-	return std::make_shared<SIndex<MetaType,S>>(*this);
-    }
-    */
     template <typename MetaT, SizeT S>
     template <class Xpr, class F>
     decltype(auto) SIndex<MetaT,S>::ifor(const Xpr& xpr, F&& f) const
@@ -203,6 +184,12 @@ namespace CNORXZ
 	return SFor<S,0,Xpr,F>(this->id(), xpr, std::forward<F>(f));
     }
 
+    template <typename MetaT, SizeT S>
+    bool SIndex<MetaT,S>::formatIsTrivial() const
+    {
+	return true;
+    }
+
     template <typename MetaType, SizeT S, class I1>
     decltype(auto) operator*(const Sptr<SIndex<MetaType,S>>& a, const Sptr<I1>& b)
     {
diff --git a/src/include/ranges/srange.h b/src/include/ranges/srange.h
index 230ef44..0ece1f7 100644
--- a/src/include/ranges/srange.h
+++ b/src/include/ranges/srange.h
@@ -65,6 +65,9 @@ namespace CNORXZ
 	template <class Xpr, class F>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const;
 
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	Sptr<RangeType> mRangePtr;
 	const MetaT* mMetaPtr;
diff --git a/src/include/ranges/urange.cc.h b/src/include/ranges/urange.cc.h
index 9a75837..978610f 100644
--- a/src/include/ranges/urange.cc.h
+++ b/src/include/ranges/urange.cc.h
@@ -193,6 +193,12 @@ namespace CNORXZ
     {
 	return For<0,Xpr,F>(this->pmax().val(), this->id(), xpr, std::forward<F>(f));
     }
+
+    template <typename MetaT>
+    bool UIndex<MetaT>::formatIsTrivial() const
+    {
+	return true;
+    }
     
     template <typename MetaT, class I1>
     decltype(auto) operator*(const Sptr<UIndex<MetaT>>& a, const Sptr<I1>& b)
diff --git a/src/include/ranges/urange.h b/src/include/ranges/urange.h
index d4ec151..7d5dade 100644
--- a/src/include/ranges/urange.h
+++ b/src/include/ranges/urange.h
@@ -70,6 +70,9 @@ namespace CNORXZ
 	template <class Xpr, class F>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const;
 
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	Sptr<RangeType> mRangePtr;
 	const MetaT* mMetaPtr;
diff --git a/src/include/ranges/xindex.cc.h b/src/include/ranges/xindex.cc.h
index a7b6460..c73fc37 100644
--- a/src/include/ranges/xindex.cc.h
+++ b/src/include/ranges/xindex.cc.h
@@ -191,6 +191,12 @@ namespace CNORXZ
 	return DXpr<SizeT>(mI->ifor(xpr, std::forward<std::function<SizeT(SizeT,SizeT)>>(f)));
     }
 
+    template <class Index, typename Meta>
+    bool XIndex<Index,Meta>::formatIsTrivial() const
+    {
+	return mI->formatIsTrivial();
+    }
+
     template <class Index, typename Meta>
     Index& XIndex<Index,Meta>::get()
     {
diff --git a/src/include/ranges/xindex.h b/src/include/ranges/xindex.h
index fa3b32d..b60f672 100644
--- a/src/include/ranges/xindex.h
+++ b/src/include/ranges/xindex.h
@@ -61,6 +61,7 @@ namespace CNORXZ
 	virtual DXpr<SizeT> ifor(const DXpr<SizeT>& xpr,
 				 std::function<SizeT(SizeT,SizeT)>&& f) const = 0;
 
+	virtual bool formatIsTrivial() const = 0;
     };
 
     //Sptr<XIndexBase>& operator++(Sptr<XIndexBase>& i);
@@ -114,6 +115,8 @@ namespace CNORXZ
 	virtual DXpr<SizeT> ifor(const DXpr<SizeT>& xpr,
 				 std::function<SizeT(SizeT,SizeT)>&& f) const override final;
 
+	virtual bool formatIsTrivial() const override final;
+
 	Index& get();
 	const Index& get() const;
 
diff --git a/src/include/ranges/yrange.h b/src/include/ranges/yrange.h
index 62bb89b..9a57027 100644
--- a/src/include/ranges/yrange.h
+++ b/src/include/ranges/yrange.h
@@ -84,6 +84,9 @@ namespace CNORXZ
 	const YFormat& lexFormat() const;
 	YIndex& setFormat(const YFormat& bs);
 	
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
     private:
 	inline Vector<SizeT> mkFormat() const;
 	inline Vector<SizeT> mkLexFormat() const;
diff --git a/src/lib/ranges/crange.cc b/src/lib/ranges/crange.cc
index 4e95cd3..fc1924a 100644
--- a/src/lib/ranges/crange.cc
+++ b/src/lib/ranges/crange.cc
@@ -138,6 +138,11 @@ namespace CNORXZ
     {
 	return 1;
     }
+
+    bool CIndex::formatIsTrivial() const
+    {
+	return true;
+    }
     
     /*============================================================+
      |    Implementations of member functions of CRangeFactory    |
diff --git a/src/lib/ranges/dindex.cc b/src/lib/ranges/dindex.cc
index 9b059ee..9947249 100644
--- a/src/lib/ranges/dindex.cc
+++ b/src/lib/ranges/dindex.cc
@@ -181,6 +181,11 @@ namespace CNORXZ
     {
 	return mI->deepFormat();
     }
+
+    bool DIndex::formatIsTrivial() const
+    {
+	return true;
+    }
     
     DXpr<SizeT> DIndex::ifor(const DXpr<SizeT>& xpr, std::function<SizeT(SizeT,SizeT)>&& f) const
     {
diff --git a/src/lib/ranges/yrange.cc b/src/lib/ranges/yrange.cc
index 029dc60..5f816f3 100644
--- a/src/lib/ranges/yrange.cc
+++ b/src/lib/ranges/yrange.cc
@@ -400,7 +400,13 @@ namespace CNORXZ
 	}	
 	return o;
     }
-	
+
+    bool YIndex::formatIsTrivial() const
+    {
+	CXZ_ERROR("IMPLEMENT!!!");
+	return true;
+    }
+    
     const YFormat& YIndex::format() const
     {
 	return mFormat;