linked_hash_set

This library provides an hashed set with predictable iteration order, based on the insertion order of elements. It is implemented as a linked_hash_map::LinkedHashMap where the value is (), in a similar way as HashSet is implemented from HashMap in stdlib.

Comparison with std HashSet

General usage is very similar to a traditional hashed set, but this structure also maintains insertion order.

Compared to HashSet, a LinkedHashSet uses an additional doubly-linked list running through its entries. As such methods front(), pop_front(), back() and pop_back() are provided.

Comparison with IndexSet

Compared to indexmap::IndexSet, while both maintain insertion order a LinkedHashSet uses a linked list allowing performant removals that don't affect the order of the remaining elements. However, when this distinction is unimportant indexmap should be the faster option.

Example

extern crate linked_hash_set;
use linked_hash_set::LinkedHashSet;

let mut set = LinkedHashSet::new();
assert!(set.insert(234));
assert!(set.insert(123));
assert!(set.insert(345));
assert!(!set.insert(123));

assert_eq!(set.into_iter().collect::<Vec<_>>(), vec![234, 345, 123]);