StructureSwift
LazySequence
A sequence containing the same elements as a Base sequence, but on which some operations such as map and filter are implemented lazily.
@frozen struct LazySequence<Base> where Base : SequenceMembers
Typealiases
typealias ElementA type representing the sequence’s elements.
typealias ElementsA
Sequencethat can contain the same elements as this one, possibly with a simpler type.typealias IndexA type that represents a valid position in the collection.
typealias IndicesA type that represents the indices that are valid for subscripting the collection, in ascending order.
typealias IteratorA type that provides the collection’s iteration interface and encapsulates its iteration state.
typealias SubSequenceA collection representing a contiguous subrange of this collection’s elements. The subsequence shares indices with the original collection.
Instance Subscripts
subscript(Range<Self.Index>) -> Slice<Self>Accesses a contiguous subrange of the collection’s elements.
subscript((UnboundedRange_) -> ()) -> Self.SubSequencesubscript<R>(R) -> Self.SubSequenceAccesses the contiguous subrange of the collection’s elements specified by a range expression.
subscript(LazySequence<Base>.Index) -> LazySequence<Base>.ElementAccesses the element at
position.
Instance Properties
var count: IntThe number of elements in the collection.
var count: IntReturns the number of elements.
var elements: LazySequence<Base>.ElementsThe
Base(presumably non-lazy) sequence from whichselfwas created.var elements: SelfIdentical to
self.var endIndex: LazySequence<Base>.IndexThe collection’s “past the end” position—that is, the position one greater than the last valid subscript argument.
var first: Self.Element?The first element of the collection.
var indices: LazySequence<Base>.IndicesThe indices that are valid for subscripting the collection, in ascending order.
var isEmpty: BoolA Boolean value indicating whether the collection is empty.
var isEmpty: BoolA Boolean value indicating whether the collection is empty.
var last: Self.Element?The last element of the collection.
var lazy: LazyCollection<Self.Elements>var lazy: Self.Elementsvar lazy: LazySequence<Self.Elements>var lazy: Self.Elementsvar lazy: LazySequence<Self>A sequence containing the same elements as this sequence, but on which some operations, such as
mapandfilter, are implemented lazily.var startIndex: LazySequence<Base>.IndexThe position of the first element in a non-empty collection.
var underestimatedCount: IntA value less than or equal to the number of elements in the collection.
var underestimatedCount: IntA value less than or equal to the number of elements in the sequence, calculated nondestructively.
var underestimatedCount: IntA value less than or equal to the number of elements in the sequence, calculated nondestructively.
Instance Methods
func allSatisfy((Self.Element) throws -> Bool) rethrows -> BoolReturns a Boolean value indicating whether every element of a sequence satisfies a given predicate.
func compactMap<ElementOfResult>((Self.Elements.Element) -> ElementOfResult?) -> LazyMapSequence<LazyFilterSequence<LazyMapSequence<Self.Elements, ElementOfResult?>>, ElementOfResult>Returns the non-
nilresults of mapping the given transformation over this sequence.func compactMap<ElementOfResult>((Self.Element) throws -> ElementOfResult?) rethrows -> [ElementOfResult]Returns an array containing the non-
nilresults of calling the given transformation with each element of this sequence.func contains(Self.Element) -> BoolReturns a Boolean value indicating whether the sequence contains the given element.
func contains(where: (Self.Element) throws -> Bool) rethrows -> BoolReturns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.
func difference<C>(from: C) -> CollectionDifference<Self.Element>Returns the difference needed to produce this collection’s ordered elements from the given collection.
func difference<C>(from: C, by: (C.Element, Self.Element) -> Bool) -> CollectionDifference<Self.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: Self.Index, to: Self.Index) -> Intfunc distance(from: Self.Index, to: Self.Index) -> IntReturns the distance between two indices.
func distance(from: LazySequence<Base>.Index, to: LazySequence<Base>.Index) -> IntReturns the distance between two indices.
func drop(while: (Self.Elements.Element) -> Bool) -> LazyDropWhileSequence<Self.Elements>Returns a lazy sequence that skips any initial elements that satisfy
predicate.func dropFirst(Int) -> DropFirstSequence<Self>Returns a sequence containing all but the given number of initial elements.
func dropLast(Int) -> [Self.Element]Returns a sequence containing all but the given number of final elements.
func elementsEqual<OtherSequence>(OtherSequence) -> BoolReturns a Boolean value indicating whether this sequence and another sequence contain the same elements in the same order.
func elementsEqual<OtherSequence>(OtherSequence, by: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> BoolReturns 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<Self>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((Self.Elements.Element) -> Bool) -> LazyFilterSequence<Self.Elements>Returns the elements of
selfthat satisfyisIncluded.func first(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the first element of the sequence that satisfies the given predicate.
func firstIndex(of: Self.Element) -> Self.Index?Returns the first index where the specified value appears in the collection.
func firstIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?Returns the first index in which an element of the collection satisfies the given predicate.
func flatMap<SegmentOfResult>((Self.Elements.Element) -> SegmentOfResult) -> LazySequence<FlattenSequence<LazyMapSequence<Self.Elements, SegmentOfResult>>>Returns the concatenated results of mapping the given transformation over this sequence.
func flatMap<SegmentOfResult>((Self.Element) throws -> SegmentOfResult) rethrows -> [SegmentOfResult.Element]Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.
func forEach((Self.Element) throws -> Void) rethrowsCalls the given closure on each element in the sequence in the same order as a
for-inloop.func formIndex(inout Self.Index, offsetBy: Int)Offsets the given index by the specified distance.
func formIndex(inout Self.Index, offsetBy: Int, limitedBy: Self.Index) -> BoolOffsets the given index by the specified distance, or so that it equals the given limiting index.
func formIndex(after: inout Self.Index)Replaces the given index with its successor.
func formIndex(before: inout Self.Index)Replaces the given index with its predecessor.
func index(Self.Index, offsetBy: Int) -> Self.Indexfunc index(Self.Index, offsetBy: Int) -> Self.IndexReturns an index that is the specified distance from the given index.
func index(LazySequence<Base>.Index, offsetBy: Int) -> LazySequence<Base>.IndexReturns an index that is the specified distance from the given index.
func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.
func index(LazySequence<Base>.Index, offsetBy: Int, limitedBy: LazySequence<Base>.Index) -> LazySequence<Base>.Index?Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.
func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.Index?Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.
func index(after: LazySequence<Base>.Index) -> LazySequence<Base>.IndexReturns the position immediately after the given index.
func index(before: LazySequence<Base>.Index) -> LazySequence<Base>.IndexReturns the position immediately before the given index.
func joined() -> LazySequence<FlattenSequence<Self.Elements>>Returns a lazy sequence that concatenates the elements of this sequence of sequences.
func joined() -> FlattenSequence<Self>Returns the elements of this sequence of sequences, concatenated.
func joined(separator: String) -> StringReturns a new string by concatenating the elements of the sequence, adding the given separator between each element.
func joined(separator: String) -> StringReturns a new string by concatenating the elements of the sequence, adding the given separator between each element.
func joined<Separator>(separator: Separator) -> JoinedSequence<Self>Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element.
func last(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the last element of the sequence that satisfies the given predicate.
func lastIndex(of: Self.Element) -> Self.Index?Returns the last index where the specified value appears in the collection.
func lastIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?Returns the index of the last element in the collection that matches the given predicate.
func lexicographicallyPrecedes<OtherSequence>(OtherSequence) -> BoolReturns 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>(OtherSequence, by: (Self.Element, Self.Element) throws -> Bool) rethrows -> BoolReturns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the given predicate to compare elements.
func makeIterator() -> LazySequence<Base>.IteratorReturns an iterator over the elements of the collection.
func map<T>((Self.Element) throws -> T) rethrows -> [T]Returns an array containing the results of mapping the given closure over the sequence’s elements.
func map<U>((Self.Element) -> U) -> LazyMapSequence<Self.Elements, U>Returns a
LazyMapSequenceover thisSequence. The elements of the result are computed lazily, each time they are read, by callingtransformfunction on a base element.func map<T>((Self.Element) throws -> T) rethrows -> [T]Returns an array containing the results of mapping the given closure over the sequence’s elements.
func max() -> Self.Element?Returns the maximum element in the sequence.
func max(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the maximum element in the sequence, using the given predicate as the comparison between elements.
func min() -> Self.Element?Returns the minimum element in the sequence.
func min(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the minimum element in the sequence, using the given predicate as the comparison between elements.
func prefix(Int) -> PrefixSequence<Self>Returns a sequence, up to the specified maximum length, containing the initial elements of the sequence.
func prefix(through: Self.Index) -> Self.SubSequenceReturns a subsequence from the start of the collection through the specified position.
func prefix(upTo: Self.Index) -> Self.SubSequenceReturns a subsequence from the start of the collection up to, but not including, the specified position.
func prefix(while: (Self.Elements.Element) -> Bool) -> LazyPrefixWhileSequence<Self.Elements>Returns a lazy sequence of the initial consecutive elements that satisfy
predicate.func randomElement() -> Self.Element?Returns a random element of the collection.
func randomElement<T>(using: inout T) -> Self.Element?Returns a random element of the collection, using the given generator as a source for randomness.
func reduce<Result>(Result, (Result, Self.Element) throws -> Result) rethrows -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reduce<Result>(into: Result, (inout Result, Self.Element) throws -> ()) rethrows -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reversed() -> [Self.Element]Returns an array containing the elements of this sequence in reverse order.
func shuffled() -> [Self.Element]Returns the elements of the sequence, shuffled.
func shuffled<T>(using: inout T) -> [Self.Element]Returns the elements of the sequence, shuffled using the given generator as a source for randomness.
func sorted() -> [Self.Element]Returns the elements of the sequence, sorted.
func sorted(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> [Self.Element]Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.
func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Self.Element) throws -> Bool) rethrows -> [ArraySlice<Self.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(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [Self.SubSequence]Returns the longest possible subsequences of the collection, in order, around elements equal to the given element.
func split(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [ArraySlice<Self.Element>]Returns the longest possible subsequences of the sequence, in order, around elements equal to the given element.
func starts<PossiblePrefix>(with: PossiblePrefix) -> BoolReturns a Boolean value indicating whether the initial elements of the sequence are the same as the elements in another sequence.
func starts<PossiblePrefix>(with: PossiblePrefix, by: (Self.Element, PossiblePrefix.Element) throws -> Bool) rethrows -> BoolReturns 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) -> [Self.Element]Returns a subsequence, up to the given maximum length, containing the final elements of the sequence.
func suffix(from: Self.Index) -> Self.SubSequenceReturns a subsequence from the specified position to the end of the collection.
func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<Self.Element>) throws -> R) rethrows -> R?Executes a closure on the sequence’s contiguous storage.
Removed Members
Instance Methods
func flatMap<ElementOfResult>((Self.Elements.Element) -> ElementOfResult?) -> LazyMapSequence<LazyFilterSequence<LazyMapSequence<Self.Elements, ElementOfResult?>>, ElementOfResult>Returns the non-
nilresults of mapping the given transformation over this sequence.func flatMap<ElementOfResult>((Self.Element) throws -> ElementOfResult?) rethrows -> [ElementOfResult]func index(of: Self.Element) -> Self.Index?Returns the first index where the specified value appears in the collection.