Looks feasible.

The forward Iter logic should mirror pretty cleanly. After yielding index i, pop i.trailing_zeros() + 1 times and descend to i - 1. Same bit-walk as get_recursive, just counting down instead of up

PackedLeaf is probably the fiddly part, but it's basically the same as forward: the stack only needs to move when crossing a chunk boundary, with the same packing_depth tweak already in place

Two cursors (front and an exclusive back) plus two stacks seems like the nicer approach. That keeps interleaved next() / next_back() cheap without re-walking from the root on every direction change. A smaller first PR could use one stack and seek_to on direction switch instead, which is probably fine given depth is bounded.

Worth pulling out a shared descend_to and mirroring the advance logic rather than duplicating the match arms. InterfaceIter is mostly just adding a back_index for the update map.

LevelIter and InterfaceIterCow can probably wait

For tests: partial packed chunks at the end, iter_from mid-list, mixed next/next_back, and pending updates. Proptest against Spec with .rev() would be a good sanity check

Happy to take a pass at an implementation

wdyt @michaelsproul

Uh oh!

Investigate implementing DoubleEndedIterator #102

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

Investigate implementing `DoubleEndedIterator` #102