Treena

Treena: Trees stored in an arena.

Yet another arena-tree?

Treena is heavily inspired by [indextree] crate, but has extra goals.

• Provide an arena to contain multiple independent trees.
  • Even when users are manipulating single trees, they may want to create temporary tree. Forest supports such use case.
  • Forest provided by treena is a true forest: root nodes of trees in an arena have no siblings relationships among each other.
• Use clear and unambiguous names.
  • Traditional function names which are often used for tree manipulation are very unclear for non-native English speakers.
    • For example, what does A.insert_before(B) mean? "insert A before B" or "insert B before A"?
    • P.insert_before(A, B) can be interpreted relatively naturally: "P (parent) inserts the node A before the node B". However, P here is completely redundant since it must be the parent of A.
  • Treena provides these functions as A.adopt(B, AsFoo) and forest.insert(A, AsFooOf(B)). They are much clearer than the traditional names.
    • For example, A.adopt(B, AdoptAs::LastChild) can be read as "the node A adopts the node B as the last child of A".
    • Another example: forest.insert(A, InsertAs::NextSiblingOf(B)) can be read as "insert the node A as the next sibling of the node B".
• Be safe and easy to debug.
  • No unsafe codes (at least for now). This means that the crate won't run into undefined behavior.
  • Using .expect() everywhere with meaningful message when it won't fail or should panic for some reason.
    • For example, if treena panics with [precondition] node must be alive, you can be aware immediately that the passed node is not alive but it violates precondition of the function.
    • Another example: if treena panics with [consistency] foobarbaz, it is sure that this is a bug of treena (not you).

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE.txt or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT.txt or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.