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Rust Collection Traits

Abstract common operations from std collections. For a working sample, check tests/group_by.rs

This crate is experimental. Better a RFC is needed to formally abstract operations (like Cpp Concept/Named requirements).

Collections in std:

  • slice: &[T], &mut [T]
  • array: [T; N]
  • sequence: Vec<T>, VecDeque<T>, LinkedList<T>
  • set: BTreeSet<T>, HashSet<T>
  • map: BTreeMap<T>, HashMap<T>
  • misc: BinaryHeap<T>

General Categories:

  • Collection: All collections, excluding associated ones.
    • AllocatorAwareCollection: Allocator-aware collections, currently there is only Vec<T, A>.
    • CapacityAwareCollection: Capacity-aware collections, those you can reserve, create with a given amount of capacity. E.g. HashSet::with_capacity
    • ContiguousCollection: Contiguous collections, where behaves like a contiguous region of memory. E.g. Vec::as_slice
    • SequentialCollection: Sequential collections, where you can traverse it in one direction, and modify at the end. E.g. VecDeque::push_back
    • DoubleEndedCollection: Double-ended collections, where you do sequential-like operations on both ends. E.g. LinkedList<T>::pop_front
    • RandomAccessCollection: Random access collections, where you can access by indices. E.g. VecDeque<T>::get
  • AssociatedCollection
    • AssociatedCapacityAwareCollection: Capacity-aware associated collections.
    • Set<S>: Set-like collections, HashSet<K, S> and BTreeSet<K>
    • OrderedSe<S>: Ordered set-like collections, BTreeSet<K>
    • Map<S>: Map-like collections, HashMap<K, V, S> and BTreeMap<K, V>
    • OrderedMap<S>: Ordered map-like collections, BTreeMap<K, V>
  • Other miscellaneous operations
    • Retainable or AssocaitedRetainable: Ability to retain specific elements.
    • Contains: Ability to test if an element is in sequence.
    • DrainFull/DrainRange/{Associated}DrainFilter: Ability to drain a specific amount of elements without drop the original collection.
    • Range/RangeMut: Ability to generate a view of original sequence.

TODOs

  • Rewrite it based on Mut/Own marker instead of individual types
    • This requires some non-robust unreached_unchecked on default implementation.
  • Find a way to constrain generic associated iterator types
    • ExactSizedIterator
    • TrustedRandomAccess
    • DoubleEndedIterator
    • Still can't propagate requirements to uppermost traits
  • Add more collection-like types, like &str, String
  • Rewrite all to associated types
  • Add T: Borrow<Q> related types?