# File nmatrix.rb, line 176
  def -(other)
    case other
    when NVector
      return super(NArray.refer(other))
    when NArray
      unless other.instance_of?(NArray)
        return other.coerce_rev( self, :- )
      end
    end
    raise TypeError,"Illegal operation: NVector - %s" % other.class
  end