# starts(with:) Returns a Boolean value indicating whether the initial elements of the sequence are the same as the elements in another sequence. ``` func starts(with possiblePrefix: PossiblePrefix) -> Bool where PossiblePrefix : Sequence, Self.Element == PossiblePrefix.Element ``` ## Parameters `possiblePrefix` A sequence to compare to this sequence. ## Return Value `true` if the initial elements of the sequence are the same as the elements of `possiblePrefix`; otherwise, `false`. If `possiblePrefix` has no elements, the return value is `true`. ## Discussion This example tests whether one countable range begins with the elements of another countable range. ``` let a = 1...3 let b = 1...10 print(b.starts(with: a)) // Prints "true" ``` Passing a sequence with no elements or an empty collection as `possiblePrefix` always results in `true`. ``` print(b.starts(with: [])) // Prints "true" ``` > Complexity: O(*m*), where *m* is the lesser of the length of the > sequence and the length of `possiblePrefix`. --- 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)