Expand description
§TreeFlat is the simplest way to build & traverse a pre-order Tree for Rust.
If you build a tree::Tree in pre-order, and display in pre-order, this is the tree for you.
No extra fluff, just a simple & performant one-trick pony.
Note: The tree depends on the build order, so is not possible to re-order the tree (changing parents or levels) in different order. So, for example, you can’t add a branch later to one in the middle (only can add after the end…).
§How it works
Instead of creating an tree::Tree of node::Node pointers, nested enums, or nested Arena-based ids,
it just stores the representation of a tree::Tree like:
. Users
├── jhon_doe
├ ├── file1.rs
├ ├── file2.rs
├── jane_doe
└────── cat.jpg… flattened in pre-order on 3 Vec, that store the data, the level/deep and the parent:
| DATA: | Users | jhon_doe | file1.rs | file2.rs | jane_doe | cat.jpg |
|---|---|---|---|---|---|---|
| LEVEL: | 0 | 1 | 2 | 2 | 1 | 2 |
| PARENT: | 0 | 0 | 1 | 1 | 0 | 4 |
This allows for the performance of Vec, on the most common operations (critically: Push items + Iterate), and very efficient iterations of node::Node::parents/node::Node::children/node::Node::siblings, because it just traverses the flat vectors.
The iterators exploit these observations:
- The children are at the right/up of the parent
- The parents are at the left/down of the children
- The siblings are all that share the same level
§Examples
use tree_flat::prelude::*;
let mut tree = Tree::with_capacity("Users", 6);
let mut root = tree.tree_root_mut();
let mut child = root.push("jhon_doe");
child.push("file1.rs");
child.push("file2.rs");
let mut child = root.push("jane_doe");
child.push("cat.jpg");
//The data is backed by vectors and arena-like ids on them:
assert_eq!(
tree.as_data(),
["Users", "jhon_doe", "file1.rs", "file2.rs", "jane_doe", "cat.jpg",]
);
assert_eq!(tree.as_level(), [0, 1, 2, 2, 1, 2,]);
assert_eq!(tree.as_parents(), [0, 0, 1, 1, 0, 4,]);
//Pretty print the tree
println!("{}", tree);
//Iterations are as inserted:
for f in &tree {
dbg!(f);
}
Inspired by the talk:
“High-performance Tree Wrangling, the APL Way” – Aaron Hsu - APL Wiki