id-arena
A simple, id-based arena.
Allocate objects and get an identifier for that object back, not a reference to the allocated object. Given an id, you can get a shared or exclusive reference to the allocated object from the arena. This id-based approach is useful for constructing mutable graph data structures.
If you want allocation to return a reference, consider the typed-arena
crate instead.
This arena does not support deletion, which makes its implementation simple
and allocation fast. If you want deletion, you need a way to solve the ABA
problem. Consider using the generational-arena
crate instead.
This crate's arenas can only contain objects of a single type T. If you
need an arena of objects with heterogeneous types, consider another crate.
#![no_std] SupportRequires the alloc nightly feature. Disable the on-by-default "std" feature:
toml
[dependencies.id-arena]
version = "2"
default-features = false
rayon SupportIf the rayon feature of this crate is activated:
toml
[dependencies]
id-arena = { version = "2", features = ["rayon"] }
then you can use rayon's support for
parallel iteration. The Arena type will have a par_iter family of
methods where appropriate.
```rust use id_arena::{Arena, Id};
type AstNodeId = Id
pub enum AstNode { Const(i64), Var(String), Add { lhs: AstNodeId, rhs: AstNodeId, }, Sub { lhs: AstNodeId, rhs: AstNodeId, }, Mul { lhs: AstNodeId, rhs: AstNodeId, }, Div { lhs: AstNodeId, rhs: AstNodeId, }, }
let mut ast_nodes = Arena::
// Create the AST for a * (b + 3).
let three = astnodes.alloc(AstNode::Const(3));
let b = astnodes.alloc(AstNode::Var("b".into()));
let bplusthree = astnodes.alloc(AstNode::Add {
lhs: b,
rhs: three,
});
let a = astnodes.alloc(AstNode::Var("a".into()));
let atimesbplusthree = astnodes.alloc(AstNode::Mul {
lhs: a,
rhs: bplus_three,
});
// Can use indexing to access allocated nodes. asserteq!(astnodes[three], AstNode::Const(3)); ```