removeColumn ::
       ColumnName  -- ^ Column to be removed
    -> RTable      -- ^ input RTable 
    -> RTable      -- ^ output RTable 
removeColumn col rtabSrc = do
      srcRtup <- rtabSrc
      let targetRtup = HM.delete col srcRtup  
      return targetRtup

-- | addColumn: adds a column to an RTable
removeColumn ::
       ColumnName  -- ^ Column to be removed
    -> RTable      -- ^ input RTable 
    -> RTable
removeColumn col rtabSrc = do
      srcRtup <- rtabSrc
      let targetRtup = HM.delete col srcRtup  
      return targetRtup

-- | addColumn: adds a column to an RTable
removeColumn col rtabSrc = do
      srcRtup <- rtabSrc
      let targetRtup = HM.delete col srcRtup  
      return targetRtup

-- | addColumn: adds a column to an RTable