diff --git a/lib/util/Lexicographic.h b/lib/util/Lexicographic.h
index b922dba5..f5c55b74 100644
--- a/lib/util/Lexicographic.h
+++ b/lib/util/Lexicographic.h
@@ -26,6 +26,25 @@ namespace Grid{
       }
     }
 
+    static inline void IndexFromCoorReversed (const std::vector<int>& coor,int &index,const std::vector<int> &dims){
+      int nd=dims.size();
+      int stride=1;
+      index=0;
+      for(int d=nd-1;d>=0;d--){
+	index = index+stride*coor[d];
+	stride=stride*dims[d];
+      }
+    }
+    static inline void CoorFromIndexReversed (std::vector<int>& coor,int index,const std::vector<int> &dims){
+      int nd= dims.size();
+      coor.resize(nd);
+      for(int d=nd-1;d>=0;d--){
+	coor[d] = index % dims[d];
+	index   = index / dims[d];
+      }
+    }
+
+
   };
 
 }