Is there a map comparator that simply retains the order of insertion?

[MartinDelVecchio]

Is there a map comparator that simply retains the order of insertion?

[MartinDelVecchio]

That would be awesome for me. And based on my week of searching for "golang ordered map JSON marshal unmarshal", I think it would be awesome for a lot of other people as well.

Thank you!

[spewspews]

In short: no. If you use a comparator that orders by insertion time then you would have to look up by insertion time as well.

I would use a slice or a doubly linked list to store the items ordered by insertion in a queue-like fashion. You could then use a map to to store indices into the slice or a pointer to the linked list node. You can then do constant time lookup and in the case of the linked list constant time removal. You iterate through the slice or linked list to get an insertion ordered loop.

[MartinDelVecchio]

My problem is that I don't do the insertions; json.Unmarshal() does. As currently written, the struct it unmarshals into uses a map[string]interface{}, which is ordered. So I need to replace that with a type that 1) supports json.Unmarshal() (and json.Marshal() ) transparently, and 2) maintains insertion order.

I see that the gods map types fully support the JSON interface, so that seems promising. I was hoping that one already spuported maintaining the insertion order, but that does not appear to be the case. I will take a look at the source to see how difficult it would be to adapt HashMap to do this.

Thanks.

[emirpasic]

@MartinDelVecchio

As @spewspews mentioned, that structure hasn't yet been implemented and I think it would be a nice addition to GoDS. It's fairly easy to implement and, once implemented, the JSON serialization/deserialization would be in that (insertion) order.

I hope to have it ready this weekend, i.e. LinkedHashMap and LinkedHashSet that maintain the insertion order.

[MartinDelVecchio]

Have you made any progress on this? I'd love to try out anything that you have.

Thanks again!

[chrischris292]

any progress?

[emirpasic]

@chrischris292 unfortunately not, i'm time-limited due to recent fatherhood. i have to take a day or two one of these weekends to clean up pull requests and implement requested features.

[emirpasic]

@MartinDelVecchio @chrischris292 sorry it took so long, but I finally found some time for this

Map data structure preserving the insertion-order.
LinkedHashMap

Set data structure preserving the insertion-order.
LinkedHashSet