···218218 It is not necessary to consume all the elements of the
219219 sequence.
220220221221+ Example ([head 4] is a parser that takes 4 lines):
222222+223223+ {[
224224+ let head n r =
225225+ r |> Buf_read.(seq line) |> Seq.take n |> List.of_seq
226226+ ]}
227227+221228 @param stop This is used before parsing each item.
222229 The sequence ends if this returns [true].
223230 The default is {!at_end_of_input}. *)