    # File lib/core/facets/module/op.rb, line 64
      def -(other)
        instance_methods = instance_methods(true).map{|m| m.to_sym}
        case other
        when Array
          subtract = instance_methods & other.map{|m| m.to_sym}
        when Module
          subtract = instance_methods & other.instance_methods(true).map{|m| m.to_sym}  # false?
        when String, Symbol
          subtract = instance_methods & [other.to_sym]
        end
        base = self
        Module.new do
          include base
          subtract.each{ |x| undef_method x }
        end
      end