Description
For all collections, provide a method drain_filter. For some discussion of the method name and signature, see rust-lang/rust#43244, especially this comment.
Status
Implemented, awaiting stabilization
- Vec, LinkedList: Tracking issue for Vec::extract_if and LinkedList::extract_if rust#43244
- BTreeMap, BTreeSet: Tracking Issue for {BTreeMap,BTreeSet}::extract_if rust#70530
- HashMap, HashSet: Tracking issue for HashMap::extract_if and HashSet::extract_if rust#59618
Unimplemented
- BinaryHeap: Add drain_filter for BinaryHeap rust#42849
- VecDeque
- String
Description
This method mutably borrows the collection and takes a predicate on the elements of the collection (e.g. values for lists and key-value pairs for maps). It then creates an iterator over the elements of the collection where the predicate returned truthfully and accessing that element in the iterator removes it from the collection. For ordered collections, it should return them in order.
Example usage
let v = vec![1, 2, 3, 4, 5, 6, 7, 8];
let primes = v.drain_filter(|n| n.is_prime()).collect::Vec<_>();
assert!(v == vec![1, 4, 6, 8]);
assert!(primes == vec![2, 3, 5, 7]);Related ideas
Also of use would be a method that finds and removes the first element matching a predicate, as it would not have to do things like pre-poop its pants in case the Drain Where iterator leaks nor would it have to traverse the entire collection if e.g. the first element checked matches the predicate.