Sequenced index

[redboltz]

Boost.MultiIndex has a sequenced index feature:
https://www.boost.org/doc/libs/1_88_0/libs/multi_index/doc/reference/seq_indices.html

This allows elements to be accessed in insertion order.
It's useful for certain queue-like structures.
If multi_index_map supported it, I would be able to remove an element by a key (Hash or BTree), even if that element is in the middle of the queue.
Do you have any plans to support this feature?

[lun3x]

Hi, yes I think this is actually fairly simple to implement. There is no "non-unique" version of a sequenced ordering, therefore it is simply a matter of swapping out the HashMap or BTreeMap lookup index for a Vec or VecDeque depending on what performance characteristics we want. I'll have a look when I have some time.

[redboltz]

Thank you for your response.
I'm currently using indexmap.

• https://docs.rs/indexmap/latest/indexmap/
• https://github.com/indexmap-rs/indexmap

However, having multiple indexes along with insertion order would clearly be much more powerful and useful.