+%************************************************************************
+%* *
+\subsection{Free variables}
+%* *
+%************************************************************************
+
+These synonyms are useful when we are thinking of free variables
+
+\begin{code}
+type FreeVars = NameSet
+
+plusFV :: FreeVars -> FreeVars -> FreeVars
+addOneFV :: FreeVars -> Name -> FreeVars
+unitFV :: Name -> FreeVars
+emptyFVs :: FreeVars
+plusFVs :: [FreeVars] -> FreeVars
+mkFVs :: [Name] -> FreeVars
+delFV :: Name -> FreeVars -> FreeVars
+delFVs :: [Name] -> FreeVars -> FreeVars
+
+isEmptyFVs = isEmptyNameSet
+emptyFVs = emptyNameSet
+plusFVs = unionManyNameSets
+plusFV = unionNameSets
+mkFVs = mkNameSet
+addOneFV = addOneToNameSet
+unitFV = unitNameSet
+delFV n s = delFromNameSet s n
+delFVs ns s = delListFromNameSet s ns
+\end{code}
+