# Iterable Implementations ## Topics ### Instance Properties [`var underestimatedCount: Int`](/documentation/Swift/RawSpan/underestimatedCount) A value less than or equal to the number of elements in the sequence, calculated nondestructively. [`var underestimatedCount: Int`](/documentation/Swift/RawSpan/underestimatedCount-41yxr) A value less than or equal to the number of elements in the sequence, calculated nondestructively. ### Instance Methods [`func makeBorrowingIterator() -> Span.BorrowingIterator`](/documentation/Swift/RawSpan/makeBorrowingIterator()) Returns a borrowing iterator over the elements of this sequence. ### Type Aliases [`typealias BorrowingIterator`](/documentation/Swift/RawSpan/BorrowingIterator) A type that provides the sequence’s iteration interface and encapsulates its iteration state. [`typealias Element`](/documentation/Swift/RawSpan/Element) A type representing the sequence’s elements. [`typealias Failure`](/documentation/Swift/RawSpan/Failure) --- 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)