diff --git a/src/multi_array_operation.h b/src/multi_array_operation.h
index 01c42f4..1cf1f72 100644
--- a/src/multi_array_operation.h
+++ b/src/multi_array_operation.h
@@ -95,19 +95,20 @@ namespace MultiArrayTools
 	public:
 	    static size_t layer() { return 0; }
 
-	    static const size_t LAYER = 0;
-	    static const size_t SIZE = OpClass::SIZE;
-	    typedef decltype(mSec.rootSteps()) ETuple;
+	    static constexpr size_t LAYER = 0;
+	    static constexpr size_t SIZE = OpClass::SIZE;
+	    typedef decltype(mSec.rootSteps()) ExtType;
 	    
 	    AssignmentExpr(OperationMaster& m, const OpClass& sec);
 
+	    AssignmentExpr(const AssignmentExpr& in) = default;
 	    AssignmentExpr(AssignmentExpr&& in) = default;
 	    //AssignmentExpr& operator=(const AssignmentExpr&& in) = default;
 	    
-	    //inline void operator()(size_t start = 0);
-	    inline void operator()(size_t start, const ETuple& last);
+	    inline void operator()(size_t start = 0);
+	    inline void operator()(size_t start, ExtType last);
 
-	    ETuple rootSteps(std::intptr_t iPtrNum = 0);
+	    auto rootSteps(std::intptr_t iPtrNum = 0) -> ExtType;
 	    
 	};
 	
@@ -178,7 +179,7 @@ namespace MultiArrayTools
 	std::tuple<size_t> rootSteps(std::intptr_t iPtrNum = 0) const; // nullptr for simple usage with decltype
 
 	template <class Expr>
-	Expr&& loop(Expr&& exp) const;
+	Expr loop(Expr exp) const;
 		
     private:
 
@@ -230,7 +231,7 @@ namespace MultiArrayTools
 	std::tuple<size_t> rootSteps(std::intptr_t iPtrNum = 0) const; // nullptr for simple usage with decltype
 
 	template <class Expr>
-	Expr&& loop(Expr&& exp) const;
+	Expr loop(Expr exp) const;
 	
     private:
 
@@ -322,8 +323,8 @@ namespace MultiArrayTools
 	    -> decltype(PackNum<sizeof...(Ops)-1>::mkStepTuple(iPtrNum, mOps));
 
 	template <class Expr>
-	auto loop(Expr&& exp) const
-	    -> decltype(PackNum<sizeof...(Ops)-1>::mkLoop( mOps, std::forward<Expr>( exp ) ))&&;
+	auto loop(Expr exp) const
+	    -> decltype(PackNum<sizeof...(Ops)-1>::mkLoop( mOps, exp));
 	
     };
     
@@ -488,13 +489,13 @@ namespace MultiArrayTools
 
     template <typename T, class OpClass, class... Ranges>
     inline void OperationMaster<T,OpClass,Ranges...>::AssignmentExpr::
-    operator()(size_t start, const ETuple& last)
+    operator()(size_t start, ExtType last)
     {
-	mM.get(start) = mSec.template get<ETuple,OpClass::SIZE-1>(last);
+	mM.get(start) = mSec.template get<ExtType,OpClass::SIZE-1>(last);
     }
     
     template <typename T, class OpClass, class... Ranges>
-    typename OperationMaster<T,OpClass,Ranges...>::AssignmentExpr::ETuple
+    typename OperationMaster<T,OpClass,Ranges...>::AssignmentExpr::ExtType
     OperationMaster<T,OpClass,Ranges...>::AssignmentExpr::
     rootSteps(std::intptr_t iPtrNum)
     {
@@ -681,9 +682,9 @@ namespace MultiArrayTools
 
     template <typename T, class... Ranges>
     template <class Expr>
-    Expr&& ConstOperationRoot<T,Ranges...>::loop(Expr&& exp) const
+    Expr ConstOperationRoot<T,Ranges...>::loop(Expr exp) const
     {
-	return std::forward<Expr>(exp);
+	return exp;
     }
     
     /***********************
@@ -784,9 +785,9 @@ namespace MultiArrayTools
 
     template <typename T, class... Ranges>
     template <class Expr>
-    Expr&& OperationRoot<T,Ranges...>::loop(Expr&& exp) const
+    Expr OperationRoot<T,Ranges...>::loop(Expr exp) const
     {
-	return std::forward<Expr>(exp);
+	return exp;
     }
     
     /*******************
@@ -842,13 +843,10 @@ namespace MultiArrayTools
 
     template <typename T, class OpFunction, class... Ops>
     template <class Expr>
-    auto Operation<T,OpFunction,Ops...>::loop(Expr&& exp) const
-	-> decltype(PackNum<sizeof...(Ops)-1>::mkLoop( mOps, std::forward<Expr>( exp ) ))&&
+    auto Operation<T,OpFunction,Ops...>::loop(Expr exp) const
+	-> decltype(PackNum<sizeof...(Ops)-1>::mkLoop( mOps, exp ))
     {
-	typedef decltype(PackNum<sizeof...(Ops)-1>::mkLoop( mOps, std::forward<Expr>( exp ) ) )
-	    LType;
-	return std::forward<LType>
-	    ( PackNum<sizeof...(Ops)-1>::mkLoop( mOps, std::forward<Expr>( exp ) ) );
+	return PackNum<sizeof...(Ops)-1>::mkLoop( mOps, exp );
     }
 
     
@@ -904,11 +902,9 @@ namespace MultiArrayTools
 
     template <typename T, class Op, class IndexType>
     template <class Expr>
-    auto Contraction<T,Op,IndexType>::loop(Expr&& exp) const -> decltype(mInd->iforh(exp))&&
+    auto Contraction<T,Op,IndexType>::loop(Expr exp) const -> decltype(mInd->iforh(exp))
     {
-	typedef decltype(mInd->iforh(exp)) LType;
-	LType&& loop = mInd->iforh(exp);
-	return std::forward<LType>( loop );
+	return mInd->iforh(exp);
     }
 
 }
diff --git a/src/ranges/container_range.h b/src/ranges/container_range.h
index 8d1240c..eb69649 100644
--- a/src/ranges/container_range.h
+++ b/src/ranges/container_range.h
@@ -90,11 +90,11 @@ namespace MultiArrayTools
 	void print(size_t offset);
 	
 	template <class Exprs>
-	auto ifor(Exprs&& exs) const
+	auto ifor(Exprs exs) const
 	    -> decltype(RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs));
 
 	template <class Exprs>
-	auto iforh(Exprs&& exs) const
+	auto iforh(Exprs exs) const
 	    -> decltype(RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs));
 
     };
@@ -377,7 +377,7 @@ namespace MultiArrayTools
 
     template <class... Indices>
     template <class Exprs>
-    auto ContainerIndex<Indices...>::ifor(Exprs&& exs) const
+    auto ContainerIndex<Indices...>::ifor(Exprs exs) const
 	-> decltype(RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs))
     {
 	return RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs);
@@ -385,7 +385,7 @@ namespace MultiArrayTools
 
     template <class... Indices>
     template <class Exprs>
-    auto ContainerIndex<Indices...>::iforh(Exprs&& exs) const
+    auto ContainerIndex<Indices...>::iforh(Exprs exs) const
 	-> decltype(RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs))
     {
 	return RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs);
diff --git a/src/ranges/multi_range.h b/src/ranges/multi_range.h
index 82e0f4a..23dfb84 100644
--- a/src/ranges/multi_range.h
+++ b/src/ranges/multi_range.h
@@ -106,11 +106,11 @@ namespace MultiArrayTools
 	void print(size_t offset);
 
 	template <class Exprs>
-	auto ifor(Exprs&& exs) const
+	auto ifor(Exprs exs) const
 	    -> decltype(RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs));
 
 	template <class Exprs>
-	auto iforh(Exprs&& exs) const
+	auto iforh(Exprs exs) const
 	    -> decltype(RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs));
 
     };
@@ -422,7 +422,7 @@ namespace MultiArrayTools
 
     template <class... Indices>
     template <class Exprs>
-    auto MultiIndex<Indices...>::ifor(Exprs&& exs) const
+    auto MultiIndex<Indices...>::ifor(Exprs exs) const
 	-> decltype(RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs))
     {
 	return RPackNum<sizeof...(Indices)-1>::mkFor(mIPack, exs);
@@ -430,7 +430,7 @@ namespace MultiArrayTools
 
     template <class... Indices>
     template <class Exprs>
-    auto MultiIndex<Indices...>::iforh(Exprs&& exs) const
+    auto MultiIndex<Indices...>::iforh(Exprs exs) const
 	-> decltype(RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs))
     {
 	return RPackNum<sizeof...(Indices)-1>::mkForh(mIPack, exs);
diff --git a/src/ranges/rpack_num.h b/src/ranges/rpack_num.h
index c49c160..d0e44c9 100644
--- a/src/ranges/rpack_num.h
+++ b/src/ranges/rpack_num.h
@@ -234,7 +234,7 @@ namespace MultiArrayHelper
 	}
 
 	template <class IndexPack, class Exprs>
-	static auto mkFor(const IndexPack& ipack, Exprs&& exs)
+	static auto mkFor(const IndexPack& ipack, Exprs exs)
 	    -> decltype(std::get<std::tuple_size<IndexPack>::value-N-1>(ipack)
 			->ifor( RPackNum<N-1>::mkFor(ipack, exs) ) )
 	{
@@ -243,7 +243,7 @@ namespace MultiArrayHelper
 	}
 
 	template <class IndexPack, class Exprs>
-	static auto mkForh(const IndexPack& ipack, Exprs&& exs)
+	static auto mkForh(const IndexPack& ipack, Exprs exs)
 	    -> decltype(std::get<std::tuple_size<IndexPack>::value-N-1>(ipack)
 			->iforh( RPackNum<N-1>::mkForh(ipack, exs) ) )
 	{
@@ -415,7 +415,7 @@ namespace MultiArrayHelper
 	}
 
 	template <class IndexPack, class Exprs>
-	static auto mkFor(const IndexPack& ipack, Exprs&& exs)
+	static auto mkFor(const IndexPack& ipack, Exprs exs)
 	    -> decltype(std::get<std::tuple_size<IndexPack>::value-1>(ipack)
 			->ifor(exs) )
 	{
@@ -423,7 +423,7 @@ namespace MultiArrayHelper
 	}
 
 	template <class IndexPack, class Exprs>
-	static auto mkForh(const IndexPack& ipack, Exprs&& exs)
+	static auto mkForh(const IndexPack& ipack, Exprs exs)
 	    -> decltype(std::get<std::tuple_size<IndexPack>::value-1>(ipack)
 			->iforh(exs) )
 	{
diff --git a/src/ranges/single_range.h b/src/ranges/single_range.h
index 51f9e31..8bd3b4d 100644
--- a/src/ranges/single_range.h
+++ b/src/ranges/single_range.h
@@ -66,11 +66,11 @@ namespace MultiArrayTools
 	void print(size_t offset);
 
 	template <class Expr>
-	auto ifor(Expr&& ex) const
+	auto ifor(Expr ex) const
 	    -> For<SingleIndex<U,TYPE>,Expr>;
 
 	template <class Expr>
-	auto iforh(Expr&& ex) const
+	auto iforh(Expr ex) const
 	    -> For<SingleIndex<U,TYPE>,Expr,ForType::HIDDEN>;
 
     };
@@ -108,7 +108,7 @@ namespace MultiArrayTools
 	
 	friend SingleRangeFactory<U,TYPE>;
 
-	static const bool defaultable = false;
+	static constexpr bool defaultable = false;
 	
     protected:
 
@@ -255,20 +255,20 @@ namespace MultiArrayTools
 
     template <typename U, SpaceType TYPE>
     template <class Expr>
-    auto SingleIndex<U,TYPE>::ifor(Expr&& ex) const
+    auto SingleIndex<U,TYPE>::ifor(Expr ex) const
 	-> For<SingleIndex<U,TYPE>,Expr>
     {
 	//static const size_t LAYER = typename Expr::LAYER; 
-	return For<SingleIndex<U,TYPE>,Expr>(this, std::forward<Expr>( ex ));
+	return For<SingleIndex<U,TYPE>,Expr>(this, ex);
     }
 
     template <typename U, SpaceType TYPE>
     template <class Expr>
-    auto SingleIndex<U,TYPE>::iforh(Expr&& ex) const
+    auto SingleIndex<U,TYPE>::iforh(Expr ex) const
 	-> For<SingleIndex<U,TYPE>,Expr,ForType::HIDDEN>
     {
 	//static const size_t LAYER = typename Expr::LAYER; 
-	return For<SingleIndex<U,TYPE>,Expr,ForType::HIDDEN>(this, std::forward<Expr>( ex ));
+	return For<SingleIndex<U,TYPE>,Expr,ForType::HIDDEN>(this, ex);
     }
 
     
diff --git a/src/xfor/exttype.h b/src/xfor/exttype.h
new file mode 100644
index 0000000..15ddb5b
--- /dev/null
+++ b/src/xfor/exttype.h
@@ -0,0 +1,178 @@
+
+#ifndef __exttype_h__
+#define __exttype_h__
+
+#include <array>
+
+namespace XFOR
+{
+
+    template <class X>
+    class MExt
+    {
+    private:
+
+	size_t mExt = 0u;
+	X mNext;
+	
+    public:
+	
+	static constexpr size_t NUM = X::NUM + 1;
+
+	MExt() = default;
+	MExt(const MExt& in) = default;
+	MExt& operator=(const MExt& in) = default;
+	MExt(MExt&& in) = default;
+	MExt& operator=(MExt&& in) = default;
+	
+	inline MExt(size_t ext, X next);
+	
+	template <size_t N>
+	inline MExt(const std::array<size_t,N>& arr);
+
+	inline size_t val() const;
+	inline const X& next() const;
+	
+	inline MExt operator+(const MExt& in) const;
+	inline MExt operator*(size_t in) const;
+	
+    };    
+
+    template <>
+    class MExt<void>
+    {
+    private:
+
+	size_t mExt = 0u;
+	
+    public:
+	
+	static constexpr size_t NUM = 0;
+
+	MExt() = default;
+	MExt(const MExt& in) = default;
+	MExt& operator=(const MExt& in) = default;
+	MExt(MExt&& in) = default;
+	MExt& operator=(MExt&& in) = default;
+	
+	inline MExt(size_t ext);
+	
+	template <size_t N>
+	inline MExt(const std::array<size_t,N>& arr);
+
+	inline size_t val() const;
+	
+	inline MExt operator+(const MExt& in) const;
+	inline MExt operator*(size_t in) const;
+
+    };    
+
+
+    template <size_t I>
+    struct Getter
+    {
+	template <class ExtType>
+	static inline size_t get(const ExtType& et)
+	{
+	    return Getter<I-1>::get(et.next());
+	}
+
+	template <class ExtType>
+	static inline auto getX(const ExtType& et)
+	    -> decltype(Getter<I-1>::get(et.next()))
+	{
+	    return Getter<I-1>::getX(et.next());
+	}	
+    };
+
+    template <>
+    struct Getter<0>
+    {
+	template <class ExtType>
+	static inline size_t get(const ExtType& et)
+	{
+	    return et.get();
+	}
+
+	template <class ExtType>
+	static inline auto getX(const ExtType& et)
+	    -> decltype(et.next())
+	{
+	    return et.next();
+	}	
+    };
+
+} // end namespace XFOR
+
+/* ========================= *
+ * ---   TEMPLATE CODE   --- *
+ * ========================= */
+
+namespace XFOR
+{
+
+    template <class X>
+    inline MExt<X>::MExt(size_t ext, X next) : mExt(ext), mNext(next) {}
+
+    template <class X>
+    template <size_t N>
+    inline MExt<X>::MExt(const std::array<size_t,N>& arr) :
+	mExt(std::get<NUM>(arr)), mNext(arr) {}
+
+    template <class X>
+    inline size_t MExt<X>::val() const
+    {
+	return mExt;
+    }
+
+    template <class X>
+    inline const X& MExt<X>::next() const
+    {
+	return mNext;
+    }
+    
+    template <class X>
+    inline MExt<X> MExt<X>::operator+(const MExt<X>& in) const
+    {
+	return MExt<X>(mExt + in.val(), mNext + in.next());
+    }
+
+    template <class X>
+    inline MExt<X> MExt<X>::operator*(size_t in) const
+    {
+	return MExt<X>(mExt * in, mNext * in);
+    }
+
+    
+    //template <>
+    inline MExt<void>::MExt(size_t ext) : mExt(ext) {}
+    
+
+    //template <>
+    template <size_t N>
+    inline MExt<void>::MExt(const std::array<size_t,N>& arr) :
+	mExt(std::get<NUM>(arr)) {}
+
+    //template <>
+    inline size_t MExt<void>::val() const
+    {
+	return mExt;
+    }
+    
+    //template <>
+    inline MExt<void> MExt<void>::operator+(const MExt<void>& in) const
+    {
+	return MExt<void>(mExt + in.val());
+    }
+
+    //template <>
+    inline MExt<void> MExt<void>::operator*(size_t in) const
+    {
+	return MExt<void>(mExt * in);
+    }
+
+
+} // end namespace XFOR
+
+
+#endif
diff --git a/src/xfor/for_params.h b/src/xfor/for_params.h
deleted file mode 100644
index 5da04b9..0000000
--- a/src/xfor/for_params.h
+++ /dev/null
@@ -1,63 +0,0 @@
-
-#ifndef __for_params_h__
-#define __for_params_h__
-
-namespace MultiArrayHelper
-{
-
-    template <typename P>
-    class ForParam
-    {
-    private:
-	size_t mVal;
-	P mNext;
-
-    public:
-	ForParam(const ForParam& last, const ForParam& ext, size_t pos);
-	inline const P& next() const;
-	inline const size_t& val() const;
-	
-    };
-
-    template <>
-    class ForParam<void>
-    {
-    private:
-	size_t mVal;
-
-    public:
-	ForParam(const ForParam& last, const ForParam& ext, size_t pos);
-	inline const size_t& val() const;
-    };
-
-    template <typename P>
-    ForParam<P>::ForParam(const ForParam& last, const ForParam& ext, size_t pos) :
-	mVal(last.val() + pos * ext.val()), mNext(last.next(), ext.next(), pos) {}
-
-    template <>
-    ForParam<void>::ForParam(const ForParam& last, const ForParam& ext, size_t pos) :
-	mVal(last.val() + pos * ext.val()) {}
-
-    template <typename P>
-    inline const P& ForParam<P>::next() const
-    {
-	return mNext;
-    }
-
-    template <typename P>
-    inline const size_t& ForParam<P>::val() const
-    {
-	return mVal;
-    }
-
-    template <>
-    inline const size_t& ForParam<void>::val() const
-    {
-	return mVal;
-    }
-
-    
-} // end namespace MultiArrayHelper
-
-
-#endif
diff --git a/src/xfor/xfor.h b/src/xfor/xfor.h
index af59b1c..41f8faa 100644
--- a/src/xfor/xfor.h
+++ b/src/xfor/xfor.h
@@ -7,7 +7,7 @@
 #include <tuple>
 #include "xfor/for_utils.h"
 #include "xfor/for_type.h"
-#include "xfor/for_params.h"
+#include "xfor/exttype.h"
 
 namespace MultiArrayHelper
 {
@@ -46,29 +46,30 @@ namespace MultiArrayHelper
 	size_t mMax;
 	Expr mExpr;
 
-	typedef decltype(mExpr.rootSteps()) FParType;
-	FParType mExt;
+	typedef decltype(mExpr.rootSteps()) ExtType;
+	ExtType mExt;
 
     public:
 
-	static size_t layer() { return Expr::layer() + 1; }
-	static const size_t LAYER = Expr::LAYER + 1;
-	static const size_t SIZE = std::remove_reference<Expr>::type::SIZE;
-	
+	static constexpr size_t LAYER = Expr::LAYER + 1;
+	static constexpr size_t SIZE = Expr::SIZE;
+
+	For(const For& in) = default;
+	For& operator=(const For& in) = default;
 	For(For&& in) = default;
 	For& operator=(For&& in) = default;
 	
 	For(const std::shared_ptr<IndexClass>& indPtr,
-	    Expr&& expr);
+	    Expr expr);
 
 	For(const IndexClass* indPtr,
-	    Expr&& expr);
+	    Expr expr);
 
 	
-	inline void operator()(size_t mlast, const FParType& last) const;
+	inline void operator()(size_t mlast, ExtType last) const;
 	inline void operator()(size_t mlast = 0) const;
 
-	FParType rootSteps(std::intptr_t iPtrNum = 0) const;
+	auto rootSteps(std::intptr_t iPtrNum = 0) const -> ExtType;
 	    
     };
 
@@ -92,7 +93,7 @@ namespace MultiArrayHelper
 
     template <class IndexClass, class Expr, ForType FT>
     For<IndexClass,Expr,FT>::For(const std::shared_ptr<IndexClass>& indPtr,
-			      Expr&& expr) :
+				 Expr expr) :
 	mIndPtr(indPtr.get()), mSPos(mIndPtr->pos()), mMax(mIndPtr->max()), mExpr(expr),
 	mExt(expr.rootSteps( reinterpret_cast<std::intptr_t>( mIndPtr.get() )))
     {
@@ -103,7 +104,7 @@ namespace MultiArrayHelper
 
     template <class IndexClass, class Expr, ForType FT>
     For<IndexClass,Expr,FT>::For(const IndexClass* indPtr,
-			      Expr&& expr) :
+				 Expr expr) :
 	mIndPtr(indPtr), mSPos(mIndPtr->pos()), mMax(mIndPtr->max()),
 	mExpr(std::forward<Expr>( expr )),
 	mExt(expr.rootSteps( reinterpret_cast<std::intptr_t>( mIndPtr ) ))
@@ -115,13 +116,11 @@ namespace MultiArrayHelper
     
     template <class IndexClass, class Expr, ForType FT>
     inline void For<IndexClass,Expr,FT>::operator()(size_t mlast,
-						    const FParType& last) const
+						    const ExtType last) const
     {
 	for(size_t pos = mSPos; pos != mMax; ++pos){
-	    //const size_t mnpos = mlast * max + pos;
 	    const size_t mnpos = PosForward<FT>::value(mlast, mMax, pos);
-	    //const FParType npos = std::move( XFPackNum<SIZE-1>::mkPos(pos, mExt, last) );
-	    const FParType npos(mlast, mExt, pos);
+	    const ExtType npos = last + mExt*pos;
 	    mExpr(mnpos, npos);
 	}
     }
@@ -129,18 +128,17 @@ namespace MultiArrayHelper
     template <class IndexClass, class Expr, ForType FT>
     inline void For<IndexClass,Expr,FT>::operator()(size_t mlast) const
     {
-	const FParType last;
+	const ExtType last;
 	for(size_t pos = mSPos; pos != mMax; ++pos){
-	    //const size_t mnpos = mlast * max + pos;
 	    const size_t mnpos = PosForward<FT>::value(mlast, mMax, pos);
-	    //const FParType npos = std::move( XFPackNum<SIZE-1>::mkPos(pos, mExt, last) );
-	    const FParType npos(mlast, mExt, pos);
+	    const ExtType npos = last + mExt*pos;
 	    mExpr(mnpos, npos);
 	}
     }
     
     template <class IndexClass, class Expr, ForType FT>
-    typename For<IndexClass,Expr,FT>::FParType For<IndexClass,Expr,FT>::rootSteps(std::intptr_t iPtrNum) const
+    auto For<IndexClass,Expr,FT>::rootSteps(std::intptr_t iPtrNum) const
+	-> ExtType
     {
 	return mExpr.rootSteps(iPtrNum);
     }