# Collection Implementations ## Topics ### Instance Properties [`var endIndex: Int`](/documentation/Swift/UnsafeMutableBufferPointer/endIndex) The “past the end” position—that is, the position one greater than the last valid subscript argument. [`var first: Self.Element?`](/documentation/Swift/UnsafeMutableBufferPointer/first) The first element of the collection. [`var indices: Range`](/documentation/Swift/UnsafeMutableBufferPointer/indices-swift.property) The indices that are valid for subscripting the collection, in ascending order. [`var isEmpty: Bool`](/documentation/Swift/UnsafeMutableBufferPointer/isEmpty) A Boolean value indicating whether the buffer is empty. [`var startIndex: Int`](/documentation/Swift/UnsafeMutableBufferPointer/startIndex) The index of the first element in a nonempty buffer. [`var underestimatedCount: Int`](/documentation/Swift/UnsafeMutableBufferPointer/underestimatedCount-4ggr6) A value less than or equal to the number of elements in the collection. ### Instance Methods [`func distance(from: Int, to: Int) -> Int`](/documentation/Swift/UnsafeMutableBufferPointer/distance(from:to:)) Returns the distance between two indices. [`func drop(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/drop(while:)-37wq1) Returns a subsequence by skipping elements while `predicate` returns `true` and returning the remaining elements. [`func dropFirst(Int) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/dropFirst(_:)-1ruqu) Returns a subsequence containing all but the given number of initial elements. [`func dropLast(Int) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/dropLast(_:)-6rw2x) Returns a subsequence containing all but the specified number of final elements. [`func firstIndex(of: Self.Element) -> Self.Index?`](/documentation/Swift/UnsafeMutableBufferPointer/firstIndex(of:)) Returns the first index where the specified value appears in the collection. [`func firstIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?`](/documentation/Swift/UnsafeMutableBufferPointer/firstIndex(where:)) Returns the first index in which an element of the collection satisfies the given predicate. [`func formIndex(inout Self.Index, offsetBy: Int)`](/documentation/Swift/UnsafeMutableBufferPointer/formIndex(_:offsetBy:)) Offsets the given index by the specified distance. [`func formIndex(inout Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Bool`](/documentation/Swift/UnsafeMutableBufferPointer/formIndex(_:offsetBy:limitedBy:)) Offsets the given index by the specified distance, or so that it equals the given limiting index. [`func formIndex(after: inout Int)`](/documentation/Swift/UnsafeMutableBufferPointer/formIndex(after:)) Replaces the given index with its successor. [`func index(Int, offsetBy: Int) -> Int`](/documentation/Swift/UnsafeMutableBufferPointer/index(_:offsetBy:)) Returns an index that is the specified distance from the given index. [`func index(Int, offsetBy: Int, limitedBy: Int) -> Int?`](/documentation/Swift/UnsafeMutableBufferPointer/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 index(after: Int) -> Int`](/documentation/Swift/UnsafeMutableBufferPointer/index(after:)) Returns the position immediately after the given index. [`func index(of: Self.Element) -> Self.Index?`](/documentation/Swift/UnsafeMutableBufferPointer/index(of:)) Returns the first index where the specified value appears in the collection. [`func indices(of: Self.Element) -> RangeSet`](/documentation/Swift/UnsafeMutableBufferPointer/indices(of:)) Returns the indices of all the elements that are equal to the given element. [`func indices(where: (Self.Element) throws -> Bool) rethrows -> RangeSet`](/documentation/Swift/UnsafeMutableBufferPointer/indices(where:)) Returns the indices of all the elements that match the given predicate. [`func map((Self.Element) throws(E) -> T) throws(E) -> [T]`](/documentation/Swift/UnsafeMutableBufferPointer/map(_:)-5p6og) Returns an array containing the results of mapping the given closure over the sequence’s elements. [`func prefix(Int) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/prefix(_:)-1n69c) Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection. [`func prefix(through: Self.Index) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/prefix(through:)) Returns a subsequence from the start of the collection through the specified position. [`func prefix(upTo: Self.Index) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/prefix(upTo:)) Returns a subsequence from the start of the collection up to, but not including, the specified position. [`func prefix(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/prefix(while:)-3arjm) Returns a subsequence containing the initial elements until `predicate` returns `false` and skipping the remaining elements. [`func randomElement() -> Self.Element?`](/documentation/Swift/UnsafeMutableBufferPointer/randomElement()) Returns a random element of the collection. [`func randomElement(using: inout T) -> Self.Element?`](/documentation/Swift/UnsafeMutableBufferPointer/randomElement(using:)) Returns a random element of the collection, using the given generator as a source for randomness. [`func removingSubranges(RangeSet) -> DiscontiguousSlice`](/documentation/Swift/UnsafeMutableBufferPointer/removingSubranges(_:)) Returns a collection of the elements in this collection that are not represented by the given range set. [`func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Self.Element) throws -> Bool) rethrows -> [Self.SubSequence]`](/documentation/Swift/UnsafeMutableBufferPointer/split(maxSplits:omittingEmptySubsequences:whereSeparator:)-4pbql) Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate. [`func split(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [Self.SubSequence]`](/documentation/Swift/UnsafeMutableBufferPointer/split(separator:maxSplits:omittingEmptySubsequences:)-3dgmc) Returns the longest possible subsequences of the collection, in order, around elements equal to the given element. [`func suffix(Int) -> Self.SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/suffix(_:)-qdce) 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/UnsafeMutableBufferPointer/suffix(from:)) Returns a subsequence from the specified position to the end of the collection. ### Subscripts [`subscript(Range) -> Slice>`](/documentation/Swift/UnsafeMutableBufferPointer/subscript(_:)-13u1d) Accesses a contiguous subrange of the buffer’s elements. [`subscript(Int) -> Element`](/documentation/Swift/UnsafeMutableBufferPointer/subscript(_:)-9t9gq) Accesses the element at the specified position. ### Type Aliases [`typealias Index`](/documentation/Swift/UnsafeMutableBufferPointer/Index) A type that represents a position in the collection. [`typealias Indices`](/documentation/Swift/UnsafeMutableBufferPointer/Indices-swift.typealias) A type that represents the indices that are valid for subscripting the collection, in ascending order. [`typealias SubSequence`](/documentation/Swift/UnsafeMutableBufferPointer/SubSequence) A collection representing a contiguous subrange of this collection’s elements. The subsequence shares indices with the original collection. --- 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)