# File lib/ruport/data/table.rb, line 423
    def rename_columns(old_cols=nil,new_cols=nil)
      if block_given?
        if old_cols
          old_cols.each { |c| rename_column(c,yield(c)) }
        else
          column_names.each { |c| rename_column(c,yield(c)) }
        end
        return
      end
      
      raise ArgumentError unless old_cols

      if new_cols
        raise ArgumentError,
          "odd number of arguments" unless old_cols.size == new_cols.size
        h = Hash[*old_cols.zip(new_cols).flatten]
      else
        h = old_cols
      end
      h.each {|old,new| rename_column(old,new) }
    end