class Regexp::Expression::Conditional::Expression

def <<(exp)
  expressions.last << exp
end

def add_sequence(active_opts = {}, params = { ts: 0 })
  raise TooManyBranches.new if branches.length == 2
  params = params.merge({ conditional_level: conditional_level + 1 })
  Branch.add_to(self, params, active_opts)
end

def branches
  select { |subexp| subexp.is_a?(Sequence) }
end

def condition
  find { |subexp| subexp.is_a?(Condition) }
end

def condition=(exp)
  expressions.delete(condition)
  expressions.unshift(exp)
end

def reference
  condition.reference
end