indextree

Arena based tree structure with multithreading support

This is a fork of the indextree crate which allows to remove nodes. The original version was not capable of removing nodes as the initial idea was to drop all nodes at the same time if the lifetime of the underlying memory arena has ended.

The arena tree structure is using a single Vec, a HashMap and numerical identifiers. Every node holds an id which is mapped to an index of the vector via the HashMap. This allows to drop single nodes before the lifetime of the arena hash ended. The downside is that this disables the general multiprocessing support of the original approach as HashMaps are not thread safe itself.

There is no RefCell and mutability is handled in a way much more idiomatic to Rust through unique (&mut) access to the arena.

Example usage

```rust use indextree::Arena;

// Create a new arena let arena = &mut Arena::new();

// Add some new nodes to the arena let a = arena.newnode(1); let b = arena.newnode(2);

// Append b to a a.append(b, arena); asserteq!(b.ancestors(arena).intoiter().count(), 2);

//Access a node assert_eq!(arena[b], 2);

// Remove a node arena.removenode(a); asserteq!(b.ancestors(arena).into_iter().count(), 1);

```