A sequence containing the same elements as a `Base`

sequence, but on which some operations such as `map`

and `filter`

are implemented lazily.

SDK

- Xcode 6.0.1+

Framework

- Swift Standard Library

## Declaration

## Overview

See also:

`Lazy`

Sequence Protocol

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.

SDK

- Xcode 6.0.1+

Framework

- Swift Standard Library

See also:

`Lazy`

Sequence Protocol

`typealias Lazy`Sequence.Elements

A `Sequence`

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

`typealias Lazy`Sequence.Element

A type representing the sequence’s elements.

`typealias Lazy`Sequence.Index

A type that represents a valid position in the collection.

`typealias Lazy`Sequence.Indices

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

`typealias Lazy`Sequence.Iterator

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

`typealias Lazy`Sequence.SubSequence

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

`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: Lazy`Sequence<Base>

Identical to `self`

.

`var end`Index : 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: Default`Indices<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 is`Empty : Bool

A Boolean value indicating whether the collection is empty.

`var is`Empty : Bool

A Boolean value indicating whether the collection is empty.

`var last: Base`.Element?

The last element of the collection.

`var lazy: Lazy`Sequence<Base>

Identical to `self`

.

`var lazy: Lazy`Sequence<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 start`Index : Base.Index

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

`var underestimated`Count : Int

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

`func all`Satisfy ((Base.Element) -> Bool) -> Bool

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

`func compact`Map <ElementOfResult>((Base.Element) -> ElementOfResult?) -> LazyMapSequence<LazyFilterSequence<LazyMapSequence<Base, ElementOfResult?>>, ElementOfResult>

Returns the non-`nil`

results of mapping the given transformation over this sequence.

`func compact`Map <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) -> Collection`Difference<Base.Element>

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

`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.

`func distance(from: Lazy`Sequence<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 drop`First (Int) -> DropFirstSequence<LazySequence<Base>>

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

`func drop`First (Int) -> Slice<LazySequence<Base>>

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

`func drop`Last (Int) -> [Base.Element]

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

`func drop`Last (Int) -> Slice<LazySequence<Base>>

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

`func elements`Equal <OtherSequence>(OtherSequence) -> Bool

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

`func elements`Equal <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() -> Enumerated`Sequence<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 `is`

.

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

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

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

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

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

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

`func flat`Map <SegmentOfResult>((Base.Element) -> SegmentOfResult) -> LazySequence<FlattenSequence<LazyMapSequence<Base, SegmentOfResult>>>

Returns the concatenated results of mapping the given transformation over this sequence.

`func flat`Map <ElementOfResult>((Base.Element) -> ElementOfResult?) -> LazyMapSequence<LazyFilterSequence<LazyMapSequence<Base, ElementOfResult?>>, ElementOfResult>

Returns the non-`nil`

results of mapping the given transformation over this sequence.

`func flat`Map <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 flat`Map <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 for`Each ((Base.Element) -> Void)

Calls the given closure on each element in the sequence in the same order as a `for`

-`in`

loop.

`func form`Index (inout Base.Index, offsetBy : Int)

Offsets the given index by the specified distance.

`func form`Index (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 form`Index (after: inout Base.Index)

Replaces the given index with its successor.

`func form`Index (before: inout Base.Index)

Replaces the given index with its predecessor.

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

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

`func index(Lazy`Sequence<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: Lazy`Sequence<Base>.Index) -> LazySequence<Base>.Index

Returns the position immediately after the given index.

`func index(before: Lazy`Sequence<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.

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

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

`func joined() -> Lazy`Sequence<FlattenSequence<Base>>

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

`func joined() -> Flatten`Sequence<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) -> Joined`Sequence<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 last`Index (of: Base.Element) -> Base.Index?

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

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

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

`func lexicographically`Precedes <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 lexicographically`Precedes <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 make`Iterator () -> LazySequence<Base>.Iterator

Returns an iterator over the elements of the collection.

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

Returns a `Lazy`

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) -> Prefix`Sequence<LazySequence<Base>>

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

`func prefix(Int) -> Slice<Lazy`Sequence<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(up`To : 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 random`Element () -> Base.Element?

Returns a random element of the collection.

`func random`Element <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(max`Splits : 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(max`Splits : 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<Possible`Prefix>( 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<Possible`Prefix>( 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<Lazy`Sequence<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 with`ContiguousStorageIfAvailable <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.

`subscript<R>(R) -> Slice<Lazy`Sequence<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(Lazy`Sequence<Base>.Index) -> LazySequence<Base>.Element

Accesses the element at `position`

.

`struct Lazy`MapSequence

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 Lazy`FilterSequence

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

`struct Lazy`PrefixWhileSequence

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

`struct Lazy`DropWhileSequence

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

`typealias Lazy`Collection

A collection containing the same elements as a `Base`

collection, but on which some operations such as `map`

and `filter`

are implemented lazily.

`typealias Lazy`DropWhileCollection

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

`typealias Lazy`FilterCollection

A lazy `Collection`

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

`typealias Lazy`MapCollection

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 Lazy`PrefixWhileCollection

A lazy `${Collection}`

wrapper that includes the initial consecutive elements of an underlying collection that satisfy a predicate.