sig val more : ('a Cf_seq.t option, 'b) Cf_flow.t -> 'a Cf_seq.t -> 'b Cf_seq.t * ('a Cf_seq.t option, 'b) Cf_flow.t val last : ('a Cf_seq.t option, 'b) Cf_flow.t -> 'b Cf_seq.t end