diff --git a/src/include/operation/extensions/math.h b/src/include/operation/extensions/math.h
deleted file mode 100644
index b1f9183..0000000
--- a/src/include/operation/extensions/math.h
+++ /dev/null
@@ -1,6 +0,0 @@
-
-#ifdef regFunc1
-
-regFunc1(exp)
-
-#endif
diff --git a/src/include/operation/extensions/reg.cc.h b/src/include/operation/extensions/reg.cc.h
new file mode 100644
index 0000000..fc240c8
--- /dev/null
+++ b/src/include/operation/extensions/reg.cc.h
@@ -0,0 +1,48 @@
+
+#ifndef __cxz_reg_cc_h__
+#define __cxz_reg_cc_h__
+
+#include "reg.h"
+#include "xpr/pos_type.h"
+
+namespace CNORXZ
+{
+    template <typename T, class EPosT, SizeT... Is>
+    decltype(auto) vregi(const T* d, const EPosT& pos, std::index_sequence<Is...> is)
+    {
+	constexpr SizeT N = epos_size<EPosT>::value;
+	static_assert(N == sizeof...(Is), "got inconsistent index sequence");
+	return PseudoReg<T,N> { d[pos.val()+pos.template get<Is>().val()]... };
+    }
+    
+    template <typename T, class EPosT>
+    decltype(auto) vreg(const T* d, const EPosT& pos)
+    {
+	constexpr SizeT N = epos_size<EPosT>::value;
+	static_assert(is_epos_type<EPosT>::value, "got non-epos-type");
+	if constexpr(pos_type_is_consecutive<EPosT>::value){
+	    return *reinterpret_cast<const PseudoReg<T,N>*>
+		(d+pos.val()+pos.template get<0>().val());
+	}
+	else {
+	    return vregi(d, pos, std::make_index_sequence<N>{});
+	}
+    }
+
+    template <typename T, class EPosT>
+    decltype(auto) vreg(T* d, const EPosT& pos)
+    {
+	constexpr SizeT N = epos_size<EPosT>::value;
+	static_assert(is_epos_type<EPosT>::value, "got non-epos-type");
+	if constexpr(pos_type_is_consecutive<EPosT>::value){
+	    return *reinterpret_cast<PseudoReg<T,N>*>
+		(d+pos.val()+pos.template get<0>().val());
+	}
+	else {
+	    return vregi(d, pos, std::make_index_sequence<N>{});
+	}
+    }
+
+}
+
+#endif
diff --git a/src/include/operation/extensions/reg.h b/src/include/operation/extensions/reg.h
new file mode 100644
index 0000000..8a84f71
--- /dev/null
+++ b/src/include/operation/extensions/reg.h
@@ -0,0 +1,33 @@
+
+#ifndef __cxz_reg_h__
+#define __cxz_reg_h__
+
+#include "base/base.h"
+
+namespace CNORXZ
+{
+    // pseudo extension type to be returned if extension vector of
+    // reuqired size is not available
+    // no use of Arr = std::array here, since I want ensure that
+    // it has exactly a memory size of N
+    template <typename T, SizeT N>
+    struct PseudoReg
+    {
+	T mD[N];
+    };
+
+    template <typename T, class EPosT, SizeT... Is>
+    decltype(auto) vregi(const T* d, const EPosT& pos, std::index_sequence<Is...> is);
+
+    // specialize for all kinds of available vector registers:
+    template <typename T, class EPosT>
+    decltype(auto) vreg(const T* d, const EPosT& pos);
+
+    // specialize for all kinds of available vector registers:
+    template <typename T, class EPosT>
+    decltype(auto) vreg(T* d, const EPosT& pos);
+
+    // TODO: Maybe specialize PseudoReg (-> Reg) itself (?)
+}
+
+#endif
diff --git a/src/include/operation/op_types.cc.h b/src/include/operation/op_types.cc.h
index 6b327ff..45fd3b2 100644
--- a/src/include/operation/op_types.cc.h
+++ b/src/include/operation/op_types.cc.h
@@ -149,7 +149,14 @@ namespace CNORXZ
     constexpr decltype(auto) OpRoot<T,IndexT>::operator()(const PosT& pos) const
     {
 	if constexpr(is_epos_type<PosT>::value){
-	    return vreg(mData,pos); // distinguish between consecutive/non-consecutive
+	    if constexpr(pos_type_is_consecutive<PosT>::value){
+		return vreg(mData,pos);
+	    }
+	    else {
+		// non-consecutive data cannot be directly accessed
+		// so there is no non-const (write) access!
+		return vreg(const_cast<const T*>(mData),pos);
+	    }
 	}
 	else {
 	    return mData[pos.val()];
diff --git a/src/include/xpr/pos_type.cc.h b/src/include/xpr/pos_type.cc.h
index febcdb5..e472ded 100644
--- a/src/include/xpr/pos_type.cc.h
+++ b/src/include/xpr/pos_type.cc.h
@@ -527,6 +527,13 @@ namespace CNORXZ
 	return inext(std::index_sequence_for<OPosTs...>{});
     }
 
+    template <class BPosT, class... OPosTs>
+    template <SizeT I>
+    constexpr decltype(auto) EPos<BPosT,OPosTs...>::get() const
+    {
+	return std::get<I>(mP);
+    }
+
     template <class BPosT, class... OPosTs>
     template <SizeT... Is>
     constexpr decltype(auto) EPos<BPosT,OPosTs...>::ival(std::index_sequence<Is...> is) const
@@ -564,11 +571,11 @@ namespace CNORXZ
     }
     
     template <class OPosT1, class OPosT2, class... OPosTs>
-    constexpr bool pos_type_consecutive_2<OPosT1,OPosT2,OPosTs...>::eval()
+    constexpr bool pos_types_consecutive_2<OPosT1,OPosT2,OPosTs...>::eval()
     {
 	if constexpr(is_static_pos_type<OPosT1>::value and is_static_pos_type<OPosT2>::value){
 	    if constexpr(sizeof...(OPosTs) != 0){
-		return OPosT1().val() < OPosT2().val() and pos_type_consecutive<OPosT2,OPosTs...>::value;
+		return OPosT1().val() < OPosT2().val() and pos_types_consecutive<OPosT2,OPosTs...>::value;
 	    }
 	    else {
 		return OPosT1().val() < OPosT2().val();
diff --git a/src/include/xpr/pos_type.h b/src/include/xpr/pos_type.h
index 75b5610..152fbd4 100644
--- a/src/include/xpr/pos_type.h
+++ b/src/include/xpr/pos_type.h
@@ -245,6 +245,9 @@ namespace CNORXZ
 
 	constexpr decltype(auto) val() const;
 	constexpr decltype(auto) next() const;
+
+	template <SizeT I>
+	constexpr decltype(auto) get() const;
     };
 
     /*********************************
@@ -268,9 +271,15 @@ namespace CNORXZ
     {
 	static constexpr SizeT value = is_pos_type<PosT>::value ? 1 : 0;
     };
+
+    template <class PosT>
+    struct epos_size
+    {
+	static constexpr SizeT value = 0;
+    };
     
     template <class OPosT1, class OPosT2, class... OPosTs>
-    struct pos_type_consecutive_2
+    struct pos_types_consecutive_2
     {
     private:
 	static constexpr bool eval();
@@ -280,9 +289,9 @@ namespace CNORXZ
     };
 
     template <class OPosT1, class... OPosTs>
-    struct pos_type_consecutive
+    struct pos_types_consecutive
     {
-	static constexpr bool value = sizeof...(OPosTs) == 0 ? is_pos_type<OPosT1>::value : pos_type_consecutive_2<OPosT1,OPosTs...>::value;
+	static constexpr bool value = sizeof...(OPosTs) == 0 ? is_pos_type<OPosT1>::value : pos_types_consecutive_2<OPosT1,OPosTs...>::value;
     };
 
     template <class OPosT1, class... OPosTs>
@@ -295,7 +304,7 @@ namespace CNORXZ
 	static constexpr bool value = eval();
     };
     
-    template <class PosT> struct pos_type_is_consecutive { CXZ_CVAL_FALSE; };
+    template <class PosT> struct pos_type_is_consecutive { CXZ_CVAL_TRUE; };
 
     template <SizeT N, class BPosT, class OPosT>
     decltype(auto) mkEPos(const BPosT& a, const OPosT& b);
@@ -341,10 +350,16 @@ namespace CNORXZ
 	static constexpr SizeT value = static_pos_size<NPosT>::value + 1;
     };
 
+    template <class BPosT, class... OPosTs>
+    struct epos_size<EPos<BPosT,OPosTs...>>
+    {
+	static constexpr SizeT value = sizeof...(OPosTs);
+    };
+    
     template <class BPosT, class... OPosTs>
     struct pos_type_is_consecutive<EPos<BPosT,OPosTs...>>
     {
-	static constexpr bool value = pos_type_is_consecutive<OPosTs...>::value;
+	static constexpr bool value = pos_types_consecutive<OPosTs...>::value;
     };
 
 } // end namespace CNORXZInternal