class Regexp::Expression::SequenceOperation

abstract class

def <<(exp) 

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

def add_sequence(active_opts = {}, params = { ts: 0 }) 

def add_sequence(active_opts = {}, params = { ts: 0 })
  self.class::OPERAND.add_to(self, params, active_opts)
end

def ts 

def ts
  (head = expressions.first) ? head.ts : @ts
end