diff --git a/src/multi_array_operation.h b/src/multi_array_operation.h
index 88a7b79..75c65a9 100644
--- a/src/multi_array_operation.h
+++ b/src/multi_array_operation.h
@@ -469,7 +469,8 @@ namespace MultiArrayTools
     template <typename T, class... Ranges>
     MExt<void> ConstOperationRoot<T,Ranges...>::rootSteps(std::intptr_t iPtrNum) const
     {
-	return MExt<void>(getStepSize( getRootIndices( mIndex->info() ), iPtrNum ));
+	return MExt<void>(getStepSize( mIndex->info(), iPtrNum ));
+	//return MExt<void>(getStepSize( getRootIndices( mIndex->info() ), iPtrNum ));
     }
 
 
@@ -520,7 +521,8 @@ namespace MultiArrayTools
     template <typename T, class... Ranges>
     MExt<void> OperationRoot<T,Ranges...>::rootSteps(std::intptr_t iPtrNum) const
     {
-	return MExt<void>(getStepSize( getRootIndices( mIndex->info() ), iPtrNum ));
+	return MExt<void>(getStepSize( mIndex->info(), iPtrNum ));
+	//return MExt<void>(getStepSize( getRootIndices( mIndex->info() ), iPtrNum ));
     }
 
     template <typename T, class... Ranges>
@@ -542,7 +544,7 @@ namespace MultiArrayTools
     template <class ET>
     inline T Operation<T,OpFunction,Ops...>::get(ET pos) const
     {
-	typedef std::tuple<Ops const&...> OpTuple;
+	typedef std::tuple<Ops...> OpTuple;
 	return PackNum<sizeof...(Ops)-1>::
 	    template mkOpExpr<SIZE,T,ET,OpTuple,OpFunction>(pos, mOps);
     }
diff --git a/src/pack_num.h b/src/pack_num.h
index 9bf257b..d6510eb 100644
--- a/src/pack_num.h
+++ b/src/pack_num.h
@@ -13,14 +13,7 @@
 
 namespace MultiArrayHelper
 {
-
-    template <template <typename> class X, class Y>
-    auto together(const X<void>& x, const Y& y)
-	-> X<Y>
-    {
-	return X<Y>(x, y);
-    }
-    
+	
     template <size_t N>
     struct PackNum
     {
@@ -60,9 +53,9 @@ namespace MultiArrayHelper
 
 	template <class... Ops>
 	static auto mkSteps(std::intptr_t ii, const std::tuple<Ops...>& otp)
-	    -> decltype(together(PackNum<N-1>::mkSteps(ii, otp), std::get<N>(otp).rootSteps(ii)))
+	    -> decltype(PackNum<N-1>::mkSteps(ii, otp).extend( std::get<N>(otp).rootSteps(ii)) )
 	{
-	    return together(PackNum<N-1>::mkSteps(ii, otp), std::get<N>(otp).rootSteps(ii) );
+	    return PackNum<N-1>::mkSteps(ii, otp).extend( std::get<N>(otp).rootSteps(ii));
 	}
 	
 	template <class RootStepTuple, class IndexClass, class OpClass>
@@ -80,13 +73,13 @@ namespace MultiArrayHelper
 	    typedef typename std::remove_reference<decltype(std::get<N>(ops))>::type NextOpType;
 	    static_assert(LAST > NextOpType::SIZE, "inconsistent array positions");
 	    static constexpr size_t NEXT = LAST - NextOpType::SIZE;
-	    return PackNum<N-1>::template mkOpExpr<NEXT,ETuple,OpTuple,OpFunction,decltype(std::get<N>(ops)),Args...>
-		( pos, ops, std::get<N>(ops).get(Getter<NEXT>::template get<ETuple>( pos )), args...);
+	    return PackNum<N-1>::template mkOpExpr<NEXT,T,ETuple,OpTuple,OpFunction,T,Args...>
+		( pos, ops, std::get<N>(ops).get(Getter<NEXT>::template getX<ETuple>( pos )), args...);
 	}
 
 	template <class OpTuple, class Expr>
 	static auto mkLoop( const OpTuple& ot, Expr&& exp )
-	    -> decltype(std::get<N>(ot).loop( PackNum<N-1>::mkLoop(ot,exp) ))&&
+	    -> decltype(std::get<N>(ot).loop( PackNum<N-1>::mkLoop(ot,exp) ))
 	{
 	    return std::get<N>(ot).loop( PackNum<N-1>::mkLoop(ot,exp) );
 	}
@@ -147,13 +140,15 @@ namespace MultiArrayHelper
 	template <size_t LAST, typename T, class ETuple, class OpTuple, class OpFunction, typename... Args>
 	static inline T mkOpExpr(const ETuple& pos, const OpTuple& ops, const Args&... args)
 	{
-	    static_assert(LAST == 0, "inconsistent array positions");
-	    return OpFunction::apply(std::get<0>(ops).get(Getter<0>::template get<ETuple>( pos )), args...);
+	    typedef typename std::remove_reference<decltype(std::get<0>(ops))>::type NextOpType;
+	    static constexpr size_t NEXT = LAST - NextOpType::SIZE;
+	    static_assert(NEXT == 0, "inconsistent array positions");
+	    return OpFunction::apply(std::get<0>(ops).get(Getter<0>::template getX<ETuple>( pos )), args...);
 	}
 
 	template <class OpTuple, class Expr>
 	static auto mkLoop( const OpTuple& ot, Expr&& exp )
-	    -> decltype(std::get<0>(ot).loop( exp ))&&
+	    -> decltype(std::get<0>(ot).loop( exp ))
 	{
 	    return std::get<0>(ot).loop( exp );
 	}
diff --git a/src/ranges/index_info.cc b/src/ranges/index_info.cc
index e5372d9..eaffcc4 100644
--- a/src/ranges/index_info.cc
+++ b/src/ranges/index_info.cc
@@ -89,34 +89,22 @@ namespace MultiArrayTools
 	return out;
     }
 
-    size_t getStepSize(const std::vector<IndexInfo>& iv, const IndexInfo& j)
-    {
-	size_t ss = 1;
-	auto ii = iv.end() - 1;
-	auto end = iv.begin();
-	while(*ii != j){
-	    ss *= ii->max();
-	    --ii;
-	    if(ii == end){
-		break;
-	    }
-	}
-	return ss;
-    }
-
+    //inline size_t getStepSize(const IndexInfo& ii, std::intptr_t j)
+    
     size_t getStepSize(const std::vector<IndexInfo>& iv, std::intptr_t j)
     {
 	size_t ss = 1;
-	auto ii = iv.end() - 1;
-	auto end = iv.begin();
-	while(ii->getPtrNum() != j){
-	    ss *= ii->max();
-	    --ii;
-	    if(ii == end){
-		break;
+	for(auto ii = iv.end() - 1; ii != iv.begin(); --ii){
+	    if(ii->getPtrNum() == j){
+		return ss;
 	    }
+	    ss *= ii->max();
+	}
+	if(iv.begin()->getPtrNum() == j){
+	    return ss;
+	} else {
+	    return 0;
 	}
-	return ss;
     }
     
 } // end namespace MultiArrayTools
diff --git a/src/ranges/index_info.h b/src/ranges/index_info.h
index 82f6743..01efba3 100644
--- a/src/ranges/index_info.h
+++ b/src/ranges/index_info.h
@@ -78,7 +78,24 @@ namespace MultiArrayTools
 
     std::vector<IndexInfo> getRootIndices(const IndexInfo& info);
 
-    size_t getStepSize(const std::vector<IndexInfo>& iv, const IndexInfo& j);
+    inline size_t getStepSize(const IndexInfo& ii, std::intptr_t j)
+    {
+	if(ii.type() == IndexType::SINGLE){
+	    return ii.getPtrNum() == j ? 1 : 0;	    
+	}
+	else {
+	    size_t ss = 0;
+	    size_t sx = 1;
+	    for(size_t i = 0; i != ii.dim(); ++i){
+		const IndexInfo& itmp = *ii.getPtr(ii.dim()-i-1);
+		const size_t max = itmp.max();
+		const size_t tmp = getStepSize(itmp, j);
+		ss += tmp * sx;
+		sx *= max;
+	    }
+	    return ss;
+	}
+    }
 
     size_t getStepSize(const std::vector<IndexInfo>& iv, std::intptr_t j);
 } // end namespace MultiArrayTools
diff --git a/src/xfor/exttype.h b/src/xfor/exttype.h
index c14423e..65718b3 100644
--- a/src/xfor/exttype.h
+++ b/src/xfor/exttype.h
@@ -41,6 +41,10 @@ namespace MultiArrayHelper
 	
 	inline MExt operator+(const MExt& in) const;
 	inline MExt operator*(size_t in) const;
+
+	template <class Y>
+	auto extend(const Y& y) const -> MExt<decltype(mNext.extend(y))>
+	{ return MExt<decltype(mNext.extend(y))>(mExt, mNext.extend(y)); }
 	
     };    
 
@@ -62,7 +66,13 @@ namespace MultiArrayHelper
 	MExt& operator=(MExt&& in) = default;
 	
 	inline MExt(size_t ext);
+
+	template <class Z>
+	inline MExt(size_t y, const Z& z);
 	
+	template <class Y, class Z>
+	inline MExt(const Y& y, const Z& z);
+
 	template <size_t N>
 	inline MExt(const std::array<size_t,N>& arr);
 
@@ -72,6 +82,10 @@ namespace MultiArrayHelper
 	inline MExt operator+(const MExt& in) const;
 	inline MExt operator*(size_t in) const;
 
+	template <class Y>
+	auto extend(const Y& y) const -> MExt<Y>
+	{ return MExt<Y>(mExt,y); }
+
     };    
 
 
@@ -86,7 +100,7 @@ namespace MultiArrayHelper
 
 	template <class ExtType>
 	static inline auto getX(const ExtType& et)
-	    -> decltype(Getter<I-1>::get(et.next()))
+	    -> decltype(Getter<I-1>::getX(et.next()))
 	{
 	    return Getter<I-1>::getX(et.next());
 	}	
@@ -103,9 +117,9 @@ namespace MultiArrayHelper
 
 	template <class ExtType>
 	static inline auto getX(const ExtType& et)
-	    -> decltype(et.next())
+	    -> ExtType
 	{
-	    return et.next();
+	    return et;
 	}	
     };
 
@@ -163,7 +177,18 @@ namespace MultiArrayHelper
     
     //template <>
     inline MExt<void>::MExt(size_t ext) : mExt(ext) {}
+
+
+    //template <>
+    template <class Z>
+    inline MExt<void>::MExt(size_t y, const Z& z) :
+	mExt(z.val()) {}
     
+    //template <>
+    template <class Y, class Z>
+    inline MExt<void>::MExt(const Y& y, const Z& z) :
+	mExt(y.val()) {}
+
 
     //template <>
     template <size_t N>