About

Array-backed ordered set and map data structures in Rust, optimized for stack-allocated storage of a tiny number of elements with a fixed cap. All you need is Eq!

This crate is:

• entirely safe
• fully documented
• no_std compatible
• zero dependencies (unless you want thiserror or serde integration)

This crate is designed to be used in performance-sensitive contexts with a small number of elements, where iteration is more common than look-ups and you don't mind a fixed size. One particularly useful quirk is that elements are not recompacted upon removal: this can be very useful when replacing elements in a set or using the indexes that the elements are stored at in a semantic fashion. Iteration order is guaranteed to be stable, on a first-in-first-out basis.

If this isn't what you're after, check out one of these alternatives!

• smolset: automatically converts to a HashSet when the number of elements is too large. Unordered.
• array_map: Blazing fast, fixed size. All possible keys must be known statically.
• sparseset: Heap-allocated, great for sparse data and frequent iteration. Stable order!
• HashSet: Heap-allocated, unordered, requires Hash, unbounded size.
• BTreeSet: Heap-allocated, ordered, requires Ord, unbounded size.
• IndexMap: Heap-allocated, requires Hash, unbounded size.

This crate has a reasonable collection of convenience methods for working with both sets and maps, aiming for rough equivalence with HashMap and HashSet. If you'd like more, please submit an issue or PR!