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?