im com...

src/include/ranges/crange.cc.h

@@ -7,6 +7,23 @@
 
 namespace CNORXZ
 {
+    template <class Index>
+    decltype(auto) CIndex::format(const Sptr<Index>& ind) const
+    {
+	return ind;
+    }
+
+    template <class Index>
+    decltype(auto) CIndex::slice(const Sptr<Index>& ind) const
+    {
+	if(ind != nullptr){
+	    if(ind->dim() != 0) {
+		return Sptr<CIndex>();
+	    }
+	}
+	return std::make_shared<CIndex>(*this);
+    }
+
     template <class Xpr, class F>
     decltype(auto) CIndex::ifor(const Xpr& xpr, F&& f) const
     {

src/include/ranges/crange.h

@@ -42,6 +42,12 @@ namespace CNORXZ
 	SizeT meta() const;
 	CIndex& at(const SizeT& metaPos);
 
+	template <class Index>
+	decltype(auto) format(const Sptr<Index>& ind) const;
+
+	template <class Index>
+	decltype(auto) slice(const Sptr<Index>& ind) const;
+
 	template <class Xpr, class F = NoF>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const;
 

src/include/ranges/index_base.cc.h

@@ -101,6 +101,7 @@ namespace CNORXZ
 	return mPtrId;
     }
 
+
     /****************************
      *   Non-member functions   *
      ****************************/

src/include/ranges/index_base.h

@@ -54,6 +54,12 @@ namespace CNORXZ
 	decltype(auto) meta() const { return THIS().meta(); }
 	I& at(const MetaType& meta) { return THIS().at(meta); }
 
+	template <class Index>
+	decltype(auto) format(const Sptr<Index>& ind) const { return THIS().format(ind); }
+
+	template <class Index>
+	decltype(auto) slice(const Sptr<Index>& ind) const { return THIS().slice(ind); }
+	
 	template <class Xpr, class F = NoF>
 	decltype(auto) ifor(const Xpr& xpr, F&& f) const
 	{ return THIS().ifor(xpr,std::forward<F>(f)); }
@@ -75,6 +81,10 @@ namespace CNORXZ
 	PtrId mPtrId = 0;
     };
 
+    template <class I>
+    struct is_index
+    { static constexpr bool value = std::is_base_of<IndexInterface<I,typename I::MetaType>,I>::value; };
+    
     template <class I>
     struct index_has_const_size
     { static constexpr bool value = false; };

src/include/ranges/mrange.cc.h

@@ -406,6 +406,48 @@ namespace CNORXZ
 	return *this;
     }
 
+    template <class BlockType, class... Indices>	
+    template <class Index>
+    decltype(auto) GMIndex<BlockType,Indices...>::format(const Sptr<Index>& ind) const
+    {
+	static_assert(is_index<Index>::value, "got non-index type");
+	static_assert(has_sub<Index>::value, "try to format single index");
+	if constexpr(has_static_sub<Index>::value){
+	    static_assert(index_dim<Index>::value == NI, "got index with conflicting static dimension");
+	    typedef std::remove_reference<decltype(ind->blockSizes())>::type BT;
+	    return iter<0,NI>
+		( [&](auto i) {
+		    std::get<i>(mIPack)->format(std::get<i>(ind->pack()));
+		},
+		    [](const auto&... e) {
+			return std::make_shared<GMIndex<BT,Indices...>>
+			    (mBlockSizes, e... );
+		    } );
+	}
+	else {
+	    typedef Arr<UPos,NI> BT;
+	    auto pack = ind->pack();
+	    CXZ_ASSERT(pack.size() == NI, "attempt to format index of dimension " << NI
+		       << " using index of dimension " << bs.size());
+	    auto bs = ind->blockSizes();
+	    return iter<0,NI>
+		( [&](auto i) {
+		    return std::get<i>(mIPack)->format(pack[i]);
+		},
+		    [](const auto&... e) {
+			return std::make_shared<GMIndex<BlockType,Indices...>>
+			    (mBlockSizes, e... );
+		    } );
+	}
+    }
+    
+    template <class BlockType, class... Indices>	
+    template <class Index>
+    decltype(auto) GMIndex<BlockType,Indices...>::slice(const Sptr<Index>& ind) const
+    {
+	static_assert(is_index<Index>::value, "got non-index type");
+    }
+    
     template <class BlockType, class... Indices>	
     template <class Xpr, class F>
     constexpr decltype(auto) GMIndex<BlockType,Indices...>::ifor(const Xpr& xpr, F&& f) const

src/include/ranges/mrange.h

@@ -63,6 +63,18 @@ namespace CNORXZ
 	MetaType meta() const;
 	GMIndex& at(const MetaType& metaPos);
 	
+	template <class Index>
+	decltype(auto) format(const Sptr<Index>& ind) const;
+	// -> IndexInterface;
+	// replace index instances xor replace blockSizes of ind by that of *this
+	// return result as new instance
+
+	template <class Index>
+	decltype(auto) slice(const Sptr<Index>& ind) const;
+	// -> IndexInterface;
+	// drop index instance or drop blockSize if that if ind is Null
+	// return result as new instance
+
 	template <class Xpr, class F>
 	constexpr decltype(auto) ifor(const Xpr& xpr, F&& f) const;