object.not.predicate?

not.rb

if not defined? BasicObject
  class BasicObject
    m = %w"__id__ __send__ instance_eval == equal?"
    (instance_methods - m).each{|m| undef_method(m)}
  end
end

class NotDelegator < BasicObject
  def initialize(obj)
    @_object = obj
  end

  def method_missing(m, *args, &block)
    !@_object.send(m, *args, &block)
  end
end

class Object
  def not
    NotDelegator.new(self)
  end
end

# Example:

class Post
  attr_accessor :published

  def published?
    !!@published
  end
end

p = Post.new
puts p.published?
puts p.not.published?