In practice, however, only the ATTACH-RIGHT(i) EF and ATTACH-LEFT(i) EF transitions such that 1 ≤ i ≤ n − 1 need to be considered when parsing a string of length n: Because the number of nodes in the buffer is bounded by n, transitions with i ≥ n will always be undefined because the buffer will become empty before the first i + 1 elementary transitions can be applied.
to parse strings of length n we only need 2n − 1 transitions.