# Order Dependent Operations on Dictionary Perform order-dependent operations common to all collections, as implemented for `Dictionary`. ## Topics ### Comparing Dictionaries [`func elementsEqual(OtherSequence, by: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Dictionary/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 starts(with: PossiblePrefix, by: (Self.Element, PossiblePrefix.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Dictionary/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. [`func lexicographicallyPrecedes(OtherSequence, by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Bool`](/documentation/Swift/Dictionary/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. ### Manipulating Indices [`var startIndex: Dictionary.Index`](/documentation/Swift/Dictionary/startIndex) The position of the first element in a nonempty dictionary. [`var endIndex: Dictionary.Index`](/documentation/Swift/Dictionary/endIndex) The dictionary’s “past the end” position—that is, the position one greater than the last valid subscript argument. [`func index(after: Dictionary.Index) -> Dictionary.Index`](/documentation/Swift/Dictionary/index(after:)) Returns the position immediately after the given index. [`func formIndex(after: inout Dictionary.Index)`](/documentation/Swift/Dictionary/formIndex(after:)) Replaces the given index with its successor. [`func index(Self.Index, offsetBy: Int) -> Self.Index`](/documentation/Swift/Dictionary/index(_:offsetBy:)) Returns an index that is the specified distance from the given index. [`func formIndex(inout Self.Index, offsetBy: Int)`](/documentation/Swift/Dictionary/formIndex(_:offsetBy:)) Offsets the given index by the specified distance. [`func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?`](/documentation/Swift/Dictionary/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/Dictionary/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/Dictionary/distance(from:to:)) Returns the distance between two indices. [`var indices: DefaultIndices`](/documentation/Swift/Dictionary/indices-swift.property) The indices that are valid for subscripting the collection, in ascending order. ### Selecting Elements [`subscript(Range) -> Slice`](/documentation/Swift/Dictionary/subscript(_:)-2ny9y) Accesses a contiguous subrange of the collection’s elements. [`subscript(R) -> Self.SubSequence`](/documentation/Swift/Dictionary/subscript(_:)-4h7sk) Accesses the contiguous subrange of the collection’s elements specified by a range expression. [`subscript(UnboundedRange) -> Self.SubSequence`](/documentation/Swift/Dictionary/subscript(_:)-4al9z) [`func prefix(Int) -> Self.SubSequence`](/documentation/Swift/Dictionary/prefix(_:)) 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/Dictionary/prefix(through:)) Returns a subsequence from the start of the collection through the specified position. [`func prefix(upTo: Self.Index) -> Self.SubSequence`](/documentation/Swift/Dictionary/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/Dictionary/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/Dictionary/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/Dictionary/suffix(from:)) Returns a subsequence from the specified position to the end of the collection. ### Excluding Elements [`func dropFirst(Int) -> Self.SubSequence`](/documentation/Swift/Dictionary/dropFirst(_:)) Returns a subsequence containing all but the given number of initial elements. [`func drop(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequence`](/documentation/Swift/Dictionary/drop(while:)) Returns a subsequence by skipping elements while `predicate` returns `true` and returning the remaining elements. [`func dropLast(Int) -> Self.SubSequence`](/documentation/Swift/Dictionary/dropLast(_:)) Returns a subsequence containing all but the specified number of final elements. [`func popFirst() -> Dictionary.Element?`](/documentation/Swift/Dictionary/popFirst()) Removes and returns the first key-value pair of the dictionary if the dictionary isn’t empty. ### Transforming a Dictionary’s Elements [`func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Self.Element) throws -> Bool) rethrows -> [Self.SubSequence]`](/documentation/Swift/Dictionary/split(maxSplits:omittingEmptySubsequences:whereSeparator:)) Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate. [`func reversed() -> [Self.Element]`](/documentation/Swift/Dictionary/reversed()) Returns an array containing the elements of this sequence in reverse order. [`func withContiguousStorageIfAvailable((UnsafeBufferPointer) throws -> R) rethrows -> R?`](/documentation/Swift/Dictionary/withContiguousStorageIfAvailable(_:)) Executes a closure on the sequence’s contiguous storage. --- Copyright © 2026 Apple Inc. 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