# Order Dependent Operations on Set Perform order-dependent operations common to all collections, as implemented for `Set`. ## Topics ### Manipulating Indices [`var startIndex: Set.Index`](/documentation/Swift/Set/startIndex) The starting position for iterating members of the set. [`var endIndex: Set.Index`](/documentation/Swift/Set/endIndex) The “past the end” position for the set—that is, the position one greater than the last valid subscript argument. [`func index(after: Set.Index) -> Set.Index`](/documentation/Swift/Set/index(after:)) Returns the position immediately after the given index. [`func formIndex(after: inout Set.Index)`](/documentation/Swift/Set/formIndex(after:)) Replaces the given index with its successor. [`func index(Self.Index, offsetBy: Int) -> Self.Index`](/documentation/Swift/Set/index(_:offsetBy:)) Returns an index that is the specified distance from the given index. [`func formIndex(inout Self.Index, offsetBy: Int)`](/documentation/Swift/Set/formIndex(_:offsetBy:)) Offsets the given index by the specified distance. [`func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?`](/documentation/Swift/Set/index(_:offsetBy:limitedBy:)) Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index. [`func formIndex(inout Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Bool`](/documentation/Swift/Set/formIndex(_:offsetBy:limitedBy:)) Offsets the given index by the specified distance, or so that it equals the given limiting index. [`func distance(from: Self.Index, to: Self.Index) -> Int`](/documentation/Swift/Set/distance(from:to:)) Returns the distance between two indices. [`var indices: DefaultIndices`](/documentation/Swift/Set/indices-swift.property) The indices that are valid for subscripting the collection, in ascending order. ### Comparing Sets [`func elementsEqual(OtherSequence) -> Bool`](/documentation/Swift/Set/elementsEqual(_:)) Returns a Boolean value indicating whether this sequence and another sequence contain the same elements in the same order. [`func elementsEqual(OtherSequence, by: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Set/elementsEqual(_:by:)) Returns a Boolean value indicating whether this sequence and another sequence contain equivalent elements in the same order, using the given predicate as the equivalence test. [`func lexicographicallyPrecedes(OtherSequence) -> Bool`](/documentation/Swift/Set/lexicographicallyPrecedes(_:)) Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the less-than operator (`<`) to compare elements. [`func lexicographicallyPrecedes(OtherSequence, by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Set/lexicographicallyPrecedes(_:by:)) Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the given predicate to compare elements. [`func starts(with: PossiblePrefix) -> Bool`](/documentation/Swift/Set/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, by: (Self.Element, PossiblePrefix.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Set/starts(with:by:)) Returns a Boolean value indicating whether the initial elements of the sequence are equivalent to the elements in another sequence, using the given predicate as the equivalence test. ### Selecting Elements [`subscript(Set.Index) -> Element`](/documentation/Swift/Set/subscript(_:)) Accesses the member at the given position. [`func prefix(Int) -> Self.SubSequence`](/documentation/Swift/Set/prefix(_:)) Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection. [`func prefix(upTo: Self.Index) -> Self.SubSequence`](/documentation/Swift/Set/prefix(upTo:)) Returns a subsequence from the start of the collection up to, but not including, the specified position. [`func prefix(through: Self.Index) -> Self.SubSequence`](/documentation/Swift/Set/prefix(through:)) Returns a subsequence from the start of the collection through the specified position. [`func prefix(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequence`](/documentation/Swift/Set/prefix(while:)) Returns a subsequence containing the initial elements until `predicate` returns `false` and skipping the remaining elements. [`func suffix(Int) -> Self.SubSequence`](/documentation/Swift/Set/suffix(_:)) Returns a subsequence, up to the given maximum length, containing the final elements of the collection. [`func suffix(from: Self.Index) -> Self.SubSequence`](/documentation/Swift/Set/suffix(from:)) Returns a subsequence from the specified position to the end of the collection. ### Excluding Elements [`func drop(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequence`](/documentation/Swift/Set/drop(while:)) Returns a subsequence by skipping elements while `predicate` returns `true` and returning the remaining elements. [`func dropFirst(Int) -> Self.SubSequence`](/documentation/Swift/Set/dropFirst(_:)) Returns a subsequence containing all but the given number of initial elements. [`func dropLast(Int) -> Self.SubSequence`](/documentation/Swift/Set/dropLast(_:)) Returns a subsequence containing all but the specified number of final elements. [`func popFirst() -> Element?`](/documentation/Swift/Set/popFirst()) Removes and returns the first element of the set. ### Reversing a Set’s Elements [`func reversed() -> [Self.Element]`](/documentation/Swift/Set/reversed()) Returns an array containing the elements of this sequence in reverse order. ### Splitting and Joining Elements [`func joined() -> FlattenSequence`](/documentation/Swift/Set/joined()) Returns the elements of this sequence of sequences, concatenated. [`func joined(separator: Separator) -> JoinedSequence`](/documentation/Swift/Set/joined(separator:)-7ubey) Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element. [`func joined(separator: String) -> String`](/documentation/Swift/Set/joined(separator:)-1cko4) Returns a new string by concatenating the elements of the sequence, adding the given separator between each element. [`func split(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [Self.SubSequence]`](/documentation/Swift/Set/split(separator:maxSplits:omittingEmptySubsequences:)) Returns the longest possible subsequences of the collection, in order, around elements equal to the given element. [`func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Self.Element) throws -> Bool) rethrows -> [Self.SubSequence]`](/documentation/Swift/Set/split(maxSplits:omittingEmptySubsequences:whereSeparator:)) Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying 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)