# BidirectionalCollection Implementations ## Topics ### Instance Properties [`var last: Self.Element?`](/documentation/Swift/EnumeratedSequence/last) The last element of the collection. ### Instance Methods [`func difference(from: C, by: (C.Element, Self.Element) -> Bool) -> CollectionDifference`](/documentation/Swift/EnumeratedSequence/difference(from:by:)) Returns the difference needed to produce this collection’s ordered elements from the given collection, using the given predicate as an equivalence test. [`func distance(from: Self.Index, to: Self.Index) -> Int`](/documentation/Swift/EnumeratedSequence/distance(from:to:)-90p1a) [`func formIndex(before: inout Self.Index)`](/documentation/Swift/EnumeratedSequence/formIndex(before:)) Replaces the given index with its predecessor. [`func index(Self.Index, offsetBy: Int) -> Self.Index`](/documentation/Swift/EnumeratedSequence/index(_:offsetBy:)-5oheh) [`func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?`](/documentation/Swift/EnumeratedSequence/index(_:offsetBy:limitedBy:)-3spm1) [`func index(before: EnumeratedSequence.Index) -> EnumeratedSequence.Index`](/documentation/Swift/EnumeratedSequence/index(before:)) Returns the position immediately before the given index. [`func last(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?`](/documentation/Swift/EnumeratedSequence/last(where:)) Returns the last element of the sequence that satisfies the given predicate. [`func lastIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?`](/documentation/Swift/EnumeratedSequence/lastIndex(where:)) Returns the index of the last element in the collection that matches the given predicate. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)