alist

alist is a Rust crate that implements association lists, inspired by Lisp, as lightweight alternative to HashMap and BTreeMap. The list is backed by a Vec of key-value pairs and preserves the order of insertion. It offers unique features like bookmarks for efficient item retrieval and is particularly well-suited for small datasets or cases where insertion order matters.

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Features

• Order Preservation: Keys and values are stored in insertion order, making alist predictable and easy to iterate over.
• Bookmark API: Efficiently retrieve frequently accessed items with O(1) access when bookmarks are used and items remain unmoved.
• Flexible Key Requirements: Unlike HashMap or BTreeMap, alist requires keys to only implement Eq.
• Convenience: Includes iterators for keys, values, and entries, as well as standard collection utilities like retain, clear, and shrink.

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When to Use alist

• Small datasets where insertions and removals are infrequent.
• Applications that rely on predictable insertion order.
• When working with keys that are not Hash or Ord.

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Installation

Add alist to your Cargo.toml:

cargo add alist

or edit your Cargo.toml manually by adding:

[dependencies]
alist = "0.1"

Examples

Creating an AList and Adding Items

use alist::AList;

let mut alist = AList::new();
alist.insert("key1", 42);
alist.insert("key2", 99);

assert_eq!(alist.get("key1"), Some(&42));
assert_eq!(alist.len(), 2);

Using the Bookmark API:

use alist::{AList, Bookmark};

let mut alist = AList::new();
alist.insert("key1", 42);
alist.insert("key2", 99);

// Bookmarks' lifetime is independant of that of alists
let mut bookmark = alist.bookmark("key1").unwrap();

// Fast retrieval using bookmark
assert_eq!(alist.get(&mut bookmark), Some(&42));

Safety and Coverage

This crate contains no unsafe code.
All tests run under miri and the tests cover about 50% of the code.
You can generate the coverage report using tarpaulin.

Contributions

Contributions are always welcome! If you have ideas for new operations or improvements, feel free to open an issue or submit a pull request.

License

This crate is licensed under the MIT License. See LICENSE for more details.