def dimensionless_deleted
      use_dimension
      hash = @dim.dup
      hash.delete_if{|k,v| LIST[k].dimensionless?}
    end
def dimensionless_deleted
      use_dimension
      hash = @dim.dup
      hash.delete_if{|k,v| LIST[k].dimensionless?}
    end
(internal use)
 @visibility private