Prefix Sum Tree: rename node and child structs

[ValarDragon]

Currently I think the prefix sum tree types are a bit confusing. node is actually a pointer to a node in the tree, and child is the actual node.

I suggest we rename node to nodePtr, and child to node.

What do you think @mconcat

[mconcat]

Absolutely agreed

[jlbit]

@ValarDragon @mconcat I was trying to find some starter tickets to work but, but looks like this one was already taken care in 4bb6f34 ?

Shall we close it to avoid other people spending more time on this?

[mconcat]

Sounds good!

[ValarDragon]

Oh I didn't realize this was done lol

[ValarDragon]

Wait no, this isn't done as far as I can tell? We still have structs named Child in the logic. We should also rename ptr to something more descriptive

If you want to get started on this, I think this package can greatly be improved. E.g. a doc trying to explain code structure, laying out the logic across files better

[mariaxu1019]

I see a to do for improving the diagram in the spec, is this the only improvement that could be made? Is there anything else that could be helpful for improving the spec?