Mutable iterator on a rope. Iterators are less efficient than Rope.get on small ropes (of length <= 1024 chars).

make r i0 returns a new iterator for the rope r. It is initially at position i0.

get itr returns the character of the rope at the current position. O(1) time. This does not change the current position.

• raises Out_of_bounds

  if the position is outside the rope.

peek itr i returns the character i of the rope. If i is close to the current position of the iterator, this will in general be more efficient than get rope i.

pos itr returns the current position. It may not be a valid position of the rope. O(1) time.

incr itr moves to the next character. O(1) time.

decr itr moves to the previous character. O(1) time.

goto itr i move to position i. O(1) time but the next call to get may be slower.

mode itr i move the current position by i chars (i may be negative or null). O(1) time but the next call to get may be slower.

rope itr returns the rope from which the iterator was constructed.