class Regexp::Parser

def set(token)
  case token.token
  when :open
    open_set(token)
  when :close
    close_set
  when :negate
    negate_set
  when :range
    range(token)
  when :intersection
    intersection(token)
  else
    raise UnknownTokenError.new('CharacterSet', token)
  end
end