Generic Structure

FlattenSequence

A sequence consisting of all the elements contained in each segment contained in some Base sequence.

Declaration

@frozen struct FlattenSequence<Base> where Base : Sequence, Base.Element : Sequence

Overview

The elements of this view are a concatenation of the elements of each sequence in the base.

The joined method is always lazy, but does not implicitly confer laziness on algorithms applied to its result. In other words, for ordinary sequences s:

  • s.joined() does not create new storage

  • s.joined().map(f) maps eagerly and returns a new array

  • s.lazy.joined().map(f) maps lazily and returns a LazyMapSequence

Topics

Type Aliases

typealias FlattenSequence.Element

A type representing the sequence’s elements.

typealias FlattenSequence.Indices

A type that represents the indices that are valid for subscripting the collection, in ascending order.

Available when Base conforms to BidirectionalCollection and Base.Element conforms to BidirectionalCollection.
typealias FlattenSequence.SubSequence

A sequence that represents a contiguous subrange of the collection’s elements.

Available when Base conforms to BidirectionalCollection and Base.Element conforms to BidirectionalCollection.

Instance Properties

var count: Int

The number of elements in the collection.

var endIndex: FlattenSequence<Base>.Index

The collection’s “past the end” position.

Available when Base conforms to Collection and Base.Element conforms to Collection.
var first: Base.Element.Element?

The first element of the collection.

var indices: DefaultIndices<FlattenSequence<Base>>

The indices that are valid for subscripting the collection, in ascending order.

var isEmpty: Bool

A Boolean value indicating whether the collection is empty.

var last: Base.Element.Element?

The last element of the collection.

var lazy: LazySequence<FlattenSequence<Base>>

A sequence containing the same elements as this sequence, but on which some operations, such as map and filter, are implemented lazily.

var startIndex: FlattenSequence<Base>.Index

The position of the first element in a non-empty collection.

Available when Base conforms to Collection and Base.Element conforms to Collection.
var underestimatedCount: Int

A value less than or equal to the number of elements in the collection.

Instance Methods

func allSatisfy((Base.Element.Element) -> Bool) -> Bool

Returns a Boolean value indicating whether every element of a sequence satisfies a given predicate.

func compactMap<ElementOfResult>((Base.Element.Element) -> ElementOfResult?) -> [ElementOfResult]

Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.

func contains(Base.Element.Element) -> Bool

Returns a Boolean value indicating whether the sequence contains the given element.

Available when Element conforms to Equatable.
func contains(where: (Base.Element.Element) -> Bool) -> Bool

Returns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.

func difference<C>(from: C) -> CollectionDifference<Base.Element.Element>

Returns the difference needed to produce this collection’s ordered elements from the given collection.

Available when Element conforms to Equatable.
func difference<C>(from: C, by: (C.Element, Base.Element.Element) -> Bool) -> CollectionDifference<Base.Element.Element>

Returns the difference needed to produce this collection’s ordered elements from the given collection, using the given predicate as an equivalence test.

func distance(from: FlattenSequence<Base>.Index, to: FlattenSequence<Base>.Index) -> Int

Returns the distance between two indices.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func drop(while: (Base.Element.Element) -> Bool) -> DropWhileSequence<FlattenSequence<Base>>

Returns a sequence by skipping the initial, consecutive elements that satisfy the given predicate.

func drop(while: (Base.Element.Element) -> Bool) -> Slice<FlattenSequence<Base>>

Returns a subsequence by skipping elements while predicate returns true and returning the remaining elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func dropFirst(Int) -> DropFirstSequence<FlattenSequence<Base>>

Returns a sequence containing all but the given number of initial elements.

func dropFirst(Int) -> Slice<FlattenSequence<Base>>

Returns a subsequence containing all but the given number of initial elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func dropLast(Int) -> [Base.Element.Element]

Returns a sequence containing all but the given number of final elements.

func dropLast(Int) -> Slice<FlattenSequence<Base>>

Returns a subsequence containing all but the specified number of final elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func elementsEqual<OtherSequence>(OtherSequence) -> Bool

Returns a Boolean value indicating whether this sequence and another sequence contain the same elements in the same order.

Available when Element conforms to Equatable.
func elementsEqual<OtherSequence>(OtherSequence, by: (Base.Element.Element, OtherSequence.Element) -> Bool) -> Bool

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 enumerated() -> EnumeratedSequence<FlattenSequence<Base>>

Returns a sequence of pairs (n, x), where n represents a consecutive integer starting at zero and x represents an element of the sequence.

func filter((Base.Element.Element) -> Bool) -> [Base.Element.Element]

Returns an array containing, in order, the elements of the sequence that satisfy the given predicate.

func first(where: (Base.Element.Element) -> Bool) -> Base.Element.Element?

Returns the first element of the sequence that satisfies the given predicate.

func firstIndex(of: Base.Element.Element) -> FlattenSequence<Base>.Index?

Returns the first index where the specified value appears in the collection.

Available when Element conforms to Equatable.
func firstIndex(where: (Base.Element.Element) -> Bool) -> FlattenSequence<Base>.Index?

Returns the first index in which an element of the collection satisfies the given predicate.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func flatMap<SegmentOfResult>((Base.Element.Element) -> SegmentOfResult) -> [SegmentOfResult.Element]

Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.

func flatMap<ElementOfResult>((Base.Element.Element) -> ElementOfResult?) -> [ElementOfResult]

Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.

Deprecated
func forEach((Base.Element.Element) -> Void)

Calls the given closure on each element in the sequence in the same order as a for-in loop.

func formIndex(inout FlattenSequence<Base>.Index, offsetBy: Int)
Available when Base conforms to Collection and Base.Element conforms to Collection.
func formIndex(inout FlattenSequence<Base>.Index, offsetBy: Int, limitedBy: FlattenSequence<Base>.Index) -> Bool
Available when Base conforms to Collection and Base.Element conforms to Collection.
func formIndex(after: inout FlattenSequence<Base>.Index)

Replaces the given index with its successor.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func formIndex(before: inout FlattenSequence<Base>.Index)

Replaces the given index with its predecessor.

Available when Base conforms to BidirectionalCollection and Base.Element conforms to BidirectionalCollection.
func index(FlattenSequence<Base>.Index, offsetBy: Int) -> FlattenSequence<Base>.Index

Returns an index that is the specified distance from the given index.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func index(FlattenSequence<Base>.Index, offsetBy: Int, limitedBy: FlattenSequence<Base>.Index) -> FlattenSequence<Base>.Index?

Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func index(after: FlattenSequence<Base>.Index) -> FlattenSequence<Base>.Index

Returns the position immediately after the given index.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func index(before: FlattenSequence<Base>.Index) -> FlattenSequence<Base>.Index

Returns the position immediately before the given index.

Available when Base conforms to BidirectionalCollection and Base.Element conforms to BidirectionalCollection.
func index(of: Base.Element.Element) -> FlattenSequence<Base>.Index?

Returns the first index where the specified value appears in the collection.

Available when Element conforms to Equatable.
Deprecated
func index(where: (Base.Element.Element) -> Bool) -> FlattenSequence<Base>.Index?

Returns the first index in which an element of the collection satisfies the given predicate.

Available when Base conforms to Collection and Base.Element conforms to Collection.
Deprecated
func joined() -> FlattenSequence<FlattenSequence<Base>>

Returns the elements of this sequence of sequences, concatenated.

Available when Element conforms to Sequence.
func joined(separator: String) -> String

Returns a new string by concatenating the elements of the sequence, adding the given separator between each element.

Available when Element conforms to StringProtocol.
func joined<Separator>(separator: Separator) -> JoinedSequence<FlattenSequence<Base>>

Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element.

Available when Element conforms to Sequence.
func joined(separator: String) -> String

Returns a new string by concatenating the elements of the sequence, adding the given separator between each element.

Available when Element is String.
func last(where: (Base.Element.Element) -> Bool) -> Base.Element.Element?

Returns the last element of the sequence that satisfies the given predicate.

func lastIndex(of: Base.Element.Element) -> FlattenSequence<Base>.Index?

Returns the last index where the specified value appears in the collection.

Available when Element conforms to Equatable.
func lastIndex(where: (Base.Element.Element) -> Bool) -> FlattenSequence<Base>.Index?

Returns the index of the last element in the collection that matches the given predicate.

func lexicographicallyPrecedes<OtherSequence>(OtherSequence) -> Bool

Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the less-than operator (<) to compare elements.

Available when Element conforms to Comparable.
func lexicographicallyPrecedes<OtherSequence>(OtherSequence, by: (Base.Element.Element, Base.Element.Element) -> Bool) -> Bool

Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the given predicate to compare elements.

func makeIterator() -> FlattenSequence<Base>.Iterator

Returns an iterator over the elements of this sequence.

func map<T>((Base.Element.Element) -> T) -> [T]

Returns an array containing the results of mapping the given closure over the sequence’s elements.

func map<T>((Base.Element.Element) -> T) -> [T]

Returns an array containing the results of mapping the given closure over the sequence’s elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func max() -> Base.Element.Element?

Returns the maximum element in the sequence.

Available when Element conforms to Comparable.
func max(by: (Base.Element.Element, Base.Element.Element) -> Bool) -> Base.Element.Element?

Returns the maximum element in the sequence, using the given predicate as the comparison between elements.

func min() -> Base.Element.Element?

Returns the minimum element in the sequence.

Available when Element conforms to Comparable.
func min(by: (Base.Element.Element, Base.Element.Element) -> Bool) -> Base.Element.Element?

Returns the minimum element in the sequence, using the given predicate as the comparison between elements.

func prefix(Int) -> PrefixSequence<FlattenSequence<Base>>

Returns a sequence, up to the specified maximum length, containing the initial elements of the sequence.

func prefix(Int) -> Slice<FlattenSequence<Base>>

Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func prefix(through: FlattenSequence<Base>.Index) -> Slice<FlattenSequence<Base>>

Returns a subsequence from the start of the collection through the specified position.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func prefix(upTo: FlattenSequence<Base>.Index) -> Slice<FlattenSequence<Base>>

Returns a subsequence from the start of the collection up to, but not including, the specified position.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func prefix(while: (Base.Element.Element) -> Bool) -> [Base.Element.Element]

Returns a sequence containing the initial, consecutive elements that satisfy the given predicate.

func prefix(while: (Base.Element.Element) -> Bool) -> Slice<FlattenSequence<Base>>

Returns a subsequence containing the initial elements until predicate returns false and skipping the remaining elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func randomElement() -> Base.Element.Element?

Returns a random element of the collection.

func randomElement<T>(using: inout T) -> Base.Element.Element?

Returns a random element of the collection, using the given generator as a source for randomness.

func reduce<Result>(Result, (Result, Base.Element.Element) -> Result) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func reduce<Result>(into: Result, (inout Result, Base.Element.Element) -> ()) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func reversed() -> [Base.Element.Element]

Returns an array containing the elements of this sequence in reverse order.

func shuffled() -> [Base.Element.Element]

Returns the elements of the sequence, shuffled.

func shuffled<T>(using: inout T) -> [Base.Element.Element]

Returns the elements of the sequence, shuffled using the given generator as a source for randomness.

func sorted() -> [Base.Element.Element]

Returns the elements of the sequence, sorted.

Available when Element conforms to Comparable.
func sorted(by: (Base.Element.Element, Base.Element.Element) -> Bool) -> [Base.Element.Element]

Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.

func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Base.Element.Element) -> Bool) -> [ArraySlice<Base.Element.Element>]

Returns the longest possible subsequences of the sequence, in order, that don’t contain elements satisfying the given predicate. Elements that are used to split the sequence are not returned as part of any subsequence.

func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Base.Element.Element) -> Bool) -> [Slice<FlattenSequence<Base>>]

Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func split(separator: Base.Element.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [ArraySlice<Base.Element.Element>]

Returns the longest possible subsequences of the sequence, in order, around elements equal to the given element.

Available when Element conforms to Equatable.
func split(separator: Base.Element.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [Slice<FlattenSequence<Base>>]

Returns the longest possible subsequences of the collection, in order, around elements equal to the given element.

Available when Element conforms to Equatable.
func starts<PossiblePrefix>(with: PossiblePrefix) -> Bool

Returns a Boolean value indicating whether the initial elements of the sequence are the same as the elements in another sequence.

Available when Element conforms to Equatable.
func starts<PossiblePrefix>(with: PossiblePrefix, by: (Base.Element.Element, PossiblePrefix.Element) -> Bool) -> Bool

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 suffix(Int) -> [Base.Element.Element]

Returns a subsequence, up to the given maximum length, containing the final elements of the sequence.

func suffix(Int) -> Slice<FlattenSequence<Base>>

Returns a subsequence, up to the given maximum length, containing the final elements of the collection.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func suffix(from: FlattenSequence<Base>.Index) -> Slice<FlattenSequence<Base>>

Returns a subsequence from the specified position to the end of the collection.

Available when Base conforms to Collection and Base.Element conforms to Collection.
func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<Base.Element.Element>) -> R) -> R?

Call body(p), where p is a pointer to the collection’s contiguous storage. If no such storage exists, it is first created. If the collection does not support an internal representation in a form of contiguous storage, body is not called and nil is returned.

Subscripts

subscript<R>(R) -> Slice<FlattenSequence<Base>>

Accesses the contiguous subrange of the collection’s elements specified by a range expression.

Available when Base conforms to Collection and Base.Element conforms to Collection.
subscript((UnboundedRange_) -> ()) -> Slice<FlattenSequence<Base>>
Available when Base conforms to Collection and Base.Element conforms to Collection.
subscript(Range<FlattenSequence<Base>.Index>) -> Slice<FlattenSequence<Base>>

Accesses a contiguous subrange of the collection’s elements.

subscript(FlattenSequence<Base>.Index) -> Base.Element.Element

Accesses the element at position.

Available when Base conforms to Collection and Base.Element conforms to Collection.
subscript(Range<FlattenSequence<Base>.Index>) -> Slice<FlattenSequence<Base>>

Accesses a contiguous subrange of the collection’s elements.

Available when Base conforms to Collection and Base.Element conforms to Collection.

Structures

struct FlattenSequence.Index

A position in a FlattenCollection

Available when Base conforms to Collection and Base.Element conforms to Collection.
struct FlattenSequence.Iterator

A type that provides the sequence’s iteration interface and encapsulates its iteration state.

Relationships

Conforms To

  • BidirectionalCollection
    Conforms when Base conforms to BidirectionalCollection and Base.Element conforms to BidirectionalCollection.
  • Collection
    Conforms when Base conforms to Collection and Base.Element conforms to Collection.

See Also

Wrappers for Algorithms

struct DropFirstSequence

A sequence that lazily consumes and drops n elements from an underlying Base iterator before possibly returning the first available element.

struct DropWhileSequence

A sequence that lazily consumes and drops n elements from an underlying Base iterator before possibly returning the first available element.

struct EnumeratedSequence

An enumeration of the elements of a sequence or collection.

typealias FlattenCollection
struct JoinedSequence

A sequence that presents the elements of a base sequence of sequences concatenated using a given separator.

struct PrefixSequence

A sequence that only consumes up to n elements from an underlying Base iterator.

struct Repeated

A collection whose elements are all identical.

struct ReversedCollection

A collection that presents the elements of its base collection in reverse order.

struct StrideTo

A sequence of values formed by striding over a half-open interval.

struct StrideThrough

A sequence of values formed by striding over a closed interval.

struct UnfoldSequence

A sequence whose elements are produced via repeated applications of a closure to some mutable state.

struct Zip2Sequence

A sequence of pairs built out of two underlying sequences.