Generic Structure

LazySequence

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

Declaration

@frozen struct LazySequence<Base> where Base : Sequence

Overview

  • See also: LazySequenceProtocol

Topics

Type Aliases

typealias LazySequence.Elements

A Sequence that can contain the same elements as this one, possibly with a simpler type.

typealias LazySequence.Element

A type representing the sequence’s elements.

typealias LazySequence.Index

A type that represents a valid position in the collection.

typealias LazySequence.Indices

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

typealias LazySequence.Iterator

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

typealias LazySequence.SubSequence

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

Instance Properties

var count: Int

The number of elements in the collection.

var count: Int

Returns the number of elements.

var elements: Base

The Base (presumably non-lazy) sequence from which self was created.

var elements: LazySequence<Base>

Identical to self.

var endIndex: Base.Index

The collection’s “past the end” position—that is, the position one greater than the last valid subscript argument.

var first: Base.Element?

The first element of the collection.

var indices: Range<Base.Index>

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

var indices: DefaultIndices<LazySequence<Base>>

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

var indices: Base.Indices

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 isEmpty: Bool

A Boolean value indicating whether the collection is empty.

var last: Base.Element?

The last element of the collection.

var lazy: LazySequence<LazySequence<Base>>

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

var lazy: Base
var lazy: Base
var startIndex: Base.Index

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

var underestimatedCount: Int

A value less than or equal to the number of elements in the sequence, calculated nondestructively.

Instance Methods

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

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

func compactMap<ElementOfResult>((Base.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) -> Bool

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

func contains(where: (Base.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>

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

Beta
func difference<C>(from: C, by: (C.Element, Base.Element) -> Bool) -> CollectionDifference<Base.Element>

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

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

Returns the distance between two indices.

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

Returns a lazy sequence that skips any initial elements that satisfy predicate.

func dropFirst(Int) -> DropFirstSequence<LazySequence<Base>>

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

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

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

func dropLast(Int) -> [Base.Element]

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

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

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

func elementsEqual<OtherSequence>(OtherSequence) -> Bool

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

func elementsEqual<OtherSequence>(OtherSequence, by: (Base.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<LazySequence<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) -> Bool) -> LazyFilterSequence<Base>

Returns the elements of self that satisfy isIncluded.

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

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

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

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

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

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

func flatMap<SegmentOfResult>((Base.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) -> 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) -> Void)

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

func formIndex(inout Base.Index, offsetBy: Int)

Offsets the given index by the specified distance.

func formIndex(inout Base.Index, offsetBy: Int, limitedBy: Base.Index) -> Bool

Offsets the given index by the specified distance, or so that it equals the given limiting index.

func formIndex(after: inout Base.Index)

Replaces the given index with its successor.

func formIndex(before: inout Base.Index)

Replaces the given index with its predecessor.

func index(LazySequence<Base>.Index, offsetBy: Int) -> LazySequence<Base>.Index

Returns an index that is the specified distance from the given 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(after: LazySequence<Base>.Index) -> LazySequence<Base>.Index

Returns the position immediately after the given index.

func index(before: LazySequence<Base>.Index) -> LazySequence<Base>.Index

Returns the position immediately before the given index.

func index(of: Base.Element) -> Base.Index?

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

Deprecated
func joined() -> LazySequence<FlattenSequence<Base>>

Returns a lazy sequence that concatenates the elements of this sequence of sequences.

func joined() -> FlattenSequence<LazySequence<Base>>

Returns the elements of this sequence of sequences, concatenated.

func joined(separator: String) -> String

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

func joined<Separator>(separator: Separator) -> JoinedSequence<LazySequence<Base>>

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

func joined(separator: String) -> String

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

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

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

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

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

func lastIndex(where: (Base.Element) -> Bool) -> 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.

func lexicographicallyPrecedes<OtherSequence>(OtherSequence, by: (Base.Element, Base.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() -> LazySequence<Base>.Iterator

Returns an iterator over the elements of the collection.

func map<U>((Base.Element) -> U) -> LazyMapSequence<Base, U>

Returns a LazyMapSequence over this Sequence. The elements of the result are computed lazily, each time they are read, by calling transform function on a base element.

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

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

func max() -> Base.Element?

Returns the maximum element in the sequence.

func max(by: (Base.Element, Base.Element) -> Bool) -> Base.Element?

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

func min() -> Base.Element?

Returns the minimum element in the sequence.

func min(by: (Base.Element, Base.Element) -> Bool) -> Base.Element?

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

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

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

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

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

func prefix(through: Base.Index) -> Slice<LazySequence<Base>>

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

func prefix(upTo: Base.Index) -> Slice<LazySequence<Base>>

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

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

Returns a lazy sequence of the initial consecutive elements that satisfy predicate.

func randomElement() -> Base.Element?

Returns a random element of the collection.

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

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

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

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

func reversed() -> [Base.Element]

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

func shuffled() -> [Base.Element]

Returns the elements of the sequence, shuffled.

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

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

func sorted() -> [Base.Element]

Returns the elements of the sequence, sorted.

func sorted(by: (Base.Element, Base.Element) -> Bool) -> [Base.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) -> Bool) -> [ArraySlice<Base.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) -> Bool) -> [Slice<LazySequence<Base>>]

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

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

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

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

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

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.

func starts<PossiblePrefix>(with: PossiblePrefix, by: (Base.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]

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

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

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

func suffix(from: Base.Index) -> Slice<LazySequence<Base>>

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

func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<Base.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<LazySequence<Base>>

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

subscript(Range<Base.Index>) -> Slice<LazySequence<Base>>

Accesses a contiguous subrange of the collection’s elements.

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

Accesses the element at position.

Relationships

Conforms To

See Also

Lazy Wrappers

struct LazyMapSequence

A Sequence whose elements consist of those in a Base Sequence passed through a transform function returning Element. These elements are computed lazily, each time they’re read, by calling the transform function on a base element.

struct LazyFilterSequence

A sequence whose elements consist of the elements of some base sequence that also satisfy a given predicate.

struct LazyPrefixWhileSequence

A sequence whose elements consist of the initial consecutive elements of some base sequence that satisfy a given predicate.

struct LazyDropWhileSequence

A sequence whose elements consist of the elements that follow the initial consecutive elements of some base sequence that satisfy a given predicate.

typealias LazyCollection

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

typealias LazyDropWhileCollection

A lazy wrapper that includes the elements of an underlying collection after any initial consecutive elements that satisfy a predicate.

typealias LazyFilterCollection

A lazy Collection wrapper that includes the elements of an underlying collection that satisfy a predicate.

typealias LazyMapCollection

A Collection whose elements consist of those in a Base Collection passed through a transform function returning Element. These elements are computed lazily, each time they’re read, by calling the transform function on a base element.

typealias LazyPrefixWhileCollection

A lazy ${Collection} wrapper that includes the initial consecutive elements of an underlying collection that satisfy a predicate.

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