class Regexp::Expression::CharacterSet

def close
  self.closed = true
end

def initialize(token, options = {})
  self.negative = false
  self.closed   = false
  super
end

def negate
  self.negative = true
end

def to_s(format = :full)
  "#{text}#{'^' if negated?}#{expressions.join}]#{quantifier_affix(format)}"
end