LazyCollection

struct LazyCollection<Base : CollectionType>

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

See Also: LazySequenceType, LazyCollection

Inheritance CollectionType, Indexable, LazyCollectionType, LazySequenceType, SequenceType View Protocol Hierarchy →
Associated Types
Elements = Base

The type of the underlying collection

Index = Base.Index

A type that represents a valid position in the collection.

Valid indices consist of the position of every element and a "past the end" position that's not valid for use as a subscript.

Generator = Base.Generator

Type alias inferred.

Element = Base.Generator.Element

Type alias inferred.

Index = Base.Index

Type alias inferred.

SubSequence = LazyCollection<Slice<Base>>

Type alias inferred.
Import import Swift

Initializers

init(_:)

Construct an instance with base as its underlying Collection instance.

Declaration

init(_ base: Base)

Instance Variables

var count: Base.Index.Distance

Returns the number of elements.

Complexity: O(1) if Index conforms to RandomAccessIndexType; O(N) otherwise.

Declaration

var count: Base.Index.Distance { get }

Declared In

LazyCollection , CollectionType
var elements: Base

The underlying collection

Declaration

var elements: Base { get }
var endIndex: Base.Index

The collection's "past the end" position.

endIndex is not a valid argument to subscript, and is always reachable from startIndex by zero or more applications of successor().

Declaration

var endIndex: Base.Index { get }
var first: Base.Generator.Element?

Returns the first element of self, or nil if self is empty.

Declaration

var first: Base.Generator.Element? { get }

Declared In

LazyCollection , CollectionType
var indices: Range<Base.Index>

Returns the range of valid index values.

The result's endIndex is the same as that of self. Because Range is half-open, iterating the values of the result produces all valid subscript arguments for self, omitting its endIndex.

Declaration

var indices: Range<Base.Index> { get }

Declared In

CollectionType
var isEmpty: Bool

Returns true iff self is empty.

Declaration

var isEmpty: Bool { get }

Declared In

LazyCollection , CollectionType
var lazy: LazyCollection<Base>

Identical to self.

Declaration

var lazy: LazyCollection<Base> { get }

Declared In

LazyCollectionType , LazySequenceType
var startIndex: Base.Index

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

In an empty collection, startIndex == endIndex.

Declaration

var startIndex: Base.Index { get }

Subscripts

subscript(_: Base.Index)

Access the element at position.

Requires: position is a valid position in self and position != endIndex.

Declaration

subscript(position: Base.Index) -> Base.Generator.Element { get }
subscript(_: Range<Base.Index>)

Returns a collection representing a contiguous sub-range of self's elements.

Complexity: O(1)

Declaration

subscript(bounds: Range<Base.Index>) -> LazyCollection<Slice<Base>> { get }

Instance Methods

func contains(_:)

Returns true iff an element in self satisfies predicate.

Declaration

func contains(@noescape predicate: (Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func dropFirst()

Returns a subsequence containing all but the first element.

Complexity: O(1)

Declaration

func dropFirst() -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func dropFirst(_:)

Returns a subsequence containing all but the first n elements.

Requires: n >= 0 Complexity: O(n)

Declaration

func dropFirst(n: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func dropLast()

Returns a subsequence containing all but the last element.

Requires: self is a finite sequence. Complexity: O(self.count)

Declaration

func dropLast() -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func dropLast(_:)

Returns a subsequence containing all but the last n elements.

Requires: n >= 0 Complexity: O(self.count)

Declaration

func dropLast(n: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func elementsEqual(_:isEquivalent:)

Returns true iff self and other contain equivalent elements, using isEquivalent as the equivalence test.

Requires: isEquivalent is an equivalence relation.

Declaration

func elementsEqual<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isEquivalent: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func enumerate()

Returns a lazy SequenceType containing pairs (n, x), where ns are consecutive Ints starting at zero, and xs are the elements of base:

> for (n, c) in "Swift".characters.enumerate() {
    print("\(n): '\(c)'")
  }
0: 'S'
1: 'w'
2: 'i'
3: 'f'
4: 't'

Declaration

func enumerate() -> EnumerateSequence<LazyCollection<Base>>

Declared In

CollectionType, SequenceType
func filter(_:)

Returns the elements of self that satisfy predicate.

Note: The elements of the result are computed on-demand, as the result is used. No buffering storage is allocated and each traversal step invokes predicate on one or more underlying elements.

Declaration

func filter(predicate: (Base.Generator.Elements.Generator.Element) -> Bool) -> LazyFilterCollection<Base.Generator.Elements>

Declared In

LazyCollectionType, CollectionType, LazySequenceType, SequenceType
func flatMap<T>(_: (Base.Generator.Element) throws -> T?)

Returns an Array containing the non-nil results of mapping transform over self.

Complexity: O(M + N), where M is the length of self and N is the length of the result.

Declaration

func flatMap<T>(@noescape transform: (Base.Generator.Element) throws -> T?) rethrows -> [T]

Declared In

CollectionType, SequenceType
func flatMap<S : SequenceType>(_: (Base.Generator.Element) throws -> S)

Returns an Array containing the concatenated results of mapping transform over self.

s.flatMap(transform)

is equivalent to

Array(s.map(transform).flatten())

Complexity: O(M + N), where M is the length of self and N is the length of the result.

Declaration

func flatMap<S : SequenceType>(transform: (Base.Generator.Element) throws -> S) rethrows -> [S.Generator.Element]

Declared In

CollectionType, SequenceType
func flatMap(_:)

Returns the concatenated results of mapping transform over self. Equivalent to 

self.map(transform).flatten()

Complexity: O(1)

Declaration

func flatMap<Intermediate : CollectionType>(transform: (Base.Generator.Elements.Generator.Element) -> Intermediate) -> LazyCollection<FlattenCollection<LazyMapCollection<Base.Generator.Elements, Intermediate>>>

Declared In

LazyCollectionType, LazySequenceType
func forEach(_:)

Call body on each element in self in the same order as a for-in loop.

sequence.forEach {
  // body code
}

is similar to:

for element in sequence {
  // body code
}

Note: You cannot use the break or continue statement to exit the current call of the body closure or skip subsequent calls. Note: Using the return statement in the body closure will only exit from the current call to body, not any outer scope, and won't skip subsequent calls.

Complexity: O(self.count)

Declaration

func forEach(@noescape body: (Base.Generator.Element) throws -> Void) rethrows

Declared In

CollectionType, SequenceType
func generate()

Returns a generator over the elements of this sequence.

Complexity: O(1).

Declaration

func generate() -> Base.Generator
func indexOf(_:)

Returns the first index where predicate returns true for the corresponding value, or nil if such value is not found.

Complexity: O(self.count).

Declaration

func indexOf(@noescape predicate: (Base.Generator.Element) throws -> Bool) rethrows -> Base.Index?

Declared In

CollectionType
func lexicographicalCompare(_:isOrderedBefore:)

Returns true iff self precedes other in a lexicographical ("dictionary") ordering, using isOrderedBefore as the comparison between elements.

Note: This method implements the mathematical notion of lexicographical ordering, which has no connection to Unicode. If you are sorting strings to present to the end-user, you should use String APIs that perform localized comparison.

Requires: isOrderedBefore is a strict weak ordering over the elements of self and other.

Declaration

func lexicographicalCompare<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isOrderedBefore: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func map(_:)

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

Declaration

func map<U>(transform: (Base.Generator.Elements.Generator.Element) -> U) -> LazyMapCollection<Base.Generator.Elements, U>

Declared In

LazyCollectionType, CollectionType, LazySequenceType, SequenceType
func maxElement(_:)

Returns the maximum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Requires: isOrderedBefore is a strict weak ordering over self.

Declaration

func maxElement(@noescape isOrderedBefore: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
func minElement(_:)

Returns the minimum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Requires: isOrderedBefore is a strict weak ordering over self.

Declaration

func minElement(@noescape isOrderedBefore: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
mutating func popFirst()

If !self.isEmpty, remove the first element and return it, otherwise return nil.

Complexity: O(1)

Declaration

mutating func popFirst() -> Base.Generator.Element?

Declared In

CollectionType
mutating func popLast()

If !self.isEmpty, remove the last element and return it, otherwise return nil.

Complexity: O(self.count)

Deprecated: it will be removed in Swift 3.

Declaration

mutating func popLast() -> Base.Generator.Element?

Declared In

CollectionType
func prefix(_:)

Returns a subsequence, up to maxLength in length, containing the initial elements.

If maxLength exceeds self.count, the result contains all the elements of self.

Requires: maxLength >= 0 Complexity: O(maxLength)

Declaration

func prefix(maxLength: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func prefixThrough(_:)

Returns prefixUpTo(position.successor())

Complexity: O(1)

Declaration

func prefixThrough(position: Base.Index) -> LazyCollection<Slice<Base>>

Declared In

CollectionType
func prefixUpTo(_:)

Returns self[startIndex..<end]

Complexity: O(1)

Declaration

func prefixUpTo(end: Base.Index) -> LazyCollection<Slice<Base>>

Declared In

CollectionType
func reduce(_:combine:)

Returns the result of repeatedly calling combine with an accumulated value initialized to initial and each element of self, in turn, i.e. return combine(combine(...combine(combine(initial, self[0]), self[1]),...self[count-2]), self[count-1]).

Declaration

func reduce<T>(initial: T, @noescape combine: (T, Base.Generator.Element) throws -> T) rethrows -> T

Declared In

CollectionType, SequenceType
mutating func removeFirst()

Remove the element at startIndex and return it.

Complexity: O(1) Requires: !self.isEmpty.

Declaration

mutating func removeFirst() -> Base.Generator.Element

Declared In

CollectionType
mutating func removeFirst(_:)

Remove the first n elements.

Complexity: - O(1) if Index conforms to RandomAccessIndexType - O(n) otherwise Requires: n >= 0 && self.count >= n.

Declaration

mutating func removeFirst(n: Int)

Declared In

CollectionType
func reverse()

Returns an Array containing the elements of self in reverse order.

Complexity: O(N), where N is the length of self.

Declaration

func reverse() -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType
func sort(_:)

Returns an Array containing the sorted elements of source according to isOrderedBefore.

The sorting algorithm is not stable (can change the relative order of elements for which isOrderedBefore does not establish an order).

Requires: isOrderedBefore is a strict weak ordering over the elements in self.

Declaration

func sort(@noescape isOrderedBefore: (Base.Generator.Element, Base.Generator.Element) -> Bool) -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType
func split(_:allowEmptySlices:isSeparator:)

Returns the maximal SubSequences of self, in order, that don't contain elements satisfying the predicate isSeparator.

maxSplit: The maximum number of SubSequences to return, minus 1. If maxSplit + 1 SubSequences are returned, the last one is a suffix of self containing the remaining elements. The default value is Int.max.

allowEmptySubsequences: If true, an empty SubSequence is produced in the result for each pair of consecutive elements satisfying isSeparator. The default value is false.

Requires: maxSplit >= 0

Declaration

func split(maxSplit: Int = default, allowEmptySlices: Bool = default, @noescape isSeparator: (Base.Generator.Element) throws -> Bool) rethrows -> [LazyCollection<Slice<Base>>]

Declared In

CollectionType, SequenceType
func startsWith(_:isEquivalent:)

Returns true iff self begins with elements equivalent to those of other, using isEquivalent as the equivalence test. Returns true if other is empty.

Requires: isEquivalent is an equivalence relation.

Declaration

func startsWith<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence, @noescape isEquivalent: (Base.Generator.Element, Base.Generator.Element) throws -> Bool) rethrows -> Bool

Declared In

CollectionType, SequenceType
func suffix(_:)

Returns a slice, up to maxLength in length, containing the final elements of s.

If maxLength exceeds s.count, the result contains all the elements of s.

Requires: maxLength >= 0 Complexity: O(self.count)

Declaration

func suffix(maxLength: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType, SequenceType
func suffixFrom(_:)

Returns self[start..<endIndex]

Complexity: O(1)

Declaration

func suffixFrom(start: Base.Index) -> LazyCollection<Slice<Base>>

Declared In

CollectionType
func underestimateCount()

Returns a value less than or equal to the number of elements in self, nondestructively.

Complexity: O(N).

Declaration

func underestimateCount() -> Int

Declared In

LazyCollection, CollectionType, SequenceType

Conditionally Inherited Items

The initializers, methods, and properties listed below may be available on this type under certain conditions (such as methods that are available on Array when its elements are Equatable) or may not ever be available if that determination is beyond SwiftDoc.org's capabilities. Please open an issue on GitHub if you see something out of place!

Where Elements == Self

var elements: LazyCollection<Base>

Identical to self.

Declaration

var elements: LazyCollection<Base> { get }

Declared In

LazyCollectionType , LazySequenceType

Where Elements.Generator.Element == Generator.Element, Generator.Element : SequenceType

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> LazySequence<FlattenSequence<Base.Generator.Elements>>

Declared In

LazySequenceType

Where Elements.Index : BidirectionalIndexType

func flatMap(_:)

Returns the concatenated results of mapping transform over self. Equivalent to 

self.map(transform).flatten()

Complexity: O(1)

Declaration

func flatMap<Intermediate : CollectionType where Intermediate.Index : BidirectionalIndexType>(transform: (Base.Generator.Elements.Generator.Element) -> Intermediate) -> LazyCollection<FlattenBidirectionalCollection<LazyMapCollection<Base.Generator.Elements, Intermediate>>>

Declared In

LazyCollectionType

Where Generator.Element : CollectionType

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> FlattenCollection<LazyCollection<Base>>

Declared In

CollectionType

Where Generator.Element : CollectionType, Elements.Generator.Element : CollectionType, Generator.Element == Elements.Generator.Element

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> LazyCollection<FlattenCollection<Base.Generator.Elements>>

Declared In

LazyCollectionType

Where Generator.Element : CollectionType, Index : BidirectionalIndexType, Generator.Element.Index : BidirectionalIndexType

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> FlattenBidirectionalCollection<LazyCollection<Base>>

Declared In

CollectionType

Where Generator.Element : CollectionType, Index : BidirectionalIndexType, Generator.Element.Index : BidirectionalIndexType, Elements.Generator.Element : CollectionType, Elements.Index : BidirectionalIndexType, Elements.Generator.Element.Index : BidirectionalIndexType, Generator.Element == Elements.Generator.Element

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> LazyCollection<FlattenBidirectionalCollection<Base.Generator.Elements>>

Declared In

LazyCollectionType

Where Generator.Element : Comparable

func lexicographicalCompare(_:)

Returns true iff self precedes other in a lexicographical ("dictionary") ordering, using "<" as the comparison between elements.

Note: This method implements the mathematical notion of lexicographical ordering, which has no connection to Unicode. If you are sorting strings to present to the end-user, you should use String APIs that perform localized comparison.

Declaration

func lexicographicalCompare<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool

Declared In

CollectionType, SequenceType
func maxElement()

Returns the maximum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Declaration

func maxElement() -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
func minElement()

Returns the minimum element in self or nil if the sequence is empty.

Complexity: O(elements.count).

Declaration

func minElement() -> Base.Generator.Element?

Declared In

CollectionType, SequenceType
func sort()

Returns an Array containing the sorted elements of source.

The sorting algorithm is not stable (can change the relative order of elements that compare equal).

Requires: The less-than operator (func <) defined in the Comparable conformance is a strict weak ordering over the elements in self.

Declaration

func sort() -> [Base.Generator.Element]

Declared In

CollectionType, SequenceType

Where Generator.Element : Equatable

func contains(_:)

Returns true iff element is in self.

Declaration

func contains(element: Base.Generator.Element) -> Bool

Declared In

CollectionType, SequenceType
func elementsEqual(_:)

Returns true iff self and other contain the same elements in the same order.

Declaration

func elementsEqual<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool

Declared In

CollectionType, SequenceType
func indexOf(_:)

Returns the first index where value appears in self or nil if value is not found.

Complexity: O(self.count).

Declaration

func indexOf(element: Base.Generator.Element) -> Base.Index?

Declared In

CollectionType
func split(_:maxSplit:allowEmptySlices:)

Returns the maximal SubSequences of self, in order, around a separator element.

maxSplit: The maximum number of SubSequences to return, minus 1. If maxSplit + 1 SubSequences are returned, the last one is a suffix of self containing the remaining elements. The default value is Int.max.

allowEmptySubsequences: If true, an empty SubSequence is produced in the result for each pair of consecutive elements satisfying isSeparator. The default value is false.

Requires: maxSplit >= 0

Declaration

func split(separator: Base.Generator.Element, maxSplit: Int = default, allowEmptySlices: Bool = default) -> [LazyCollection<Slice<Base>>]

Declared In

CollectionType, SequenceType
func startsWith(_:)

Returns true iff the initial elements of self are equal to prefix. Returns true if other is empty.

Declaration

func startsWith<OtherSequence : SequenceType where OtherSequence.Generator.Element == Generator.Element>(other: OtherSequence) -> Bool

Declared In

CollectionType, SequenceType

Where Generator.Element : SequenceType

func flatten()

A concatenation of the elements of self.

Declaration

func flatten() -> FlattenSequence<LazyCollection<Base>>

Declared In

CollectionType, SequenceType
func joinWithSeparator(_:)

Returns a view, whose elements are the result of interposing a given separator between the elements of the sequence self.

For example, [[1, 2, 3], [4, 5, 6], [7, 8, 9]].joinWithSeparator([-1, -2]) yields [1, 2, 3, -1, -2, 4, 5, 6, -1, -2, 7, 8, 9].

Declaration

func joinWithSeparator<Separator : SequenceType where Separator.Generator.Element == Generator.Element.Generator.Element>(separator: Separator) -> JoinSequence<LazyCollection<Base>>

Declared In

CollectionType, SequenceType

Where Generator.Element == String

func joinWithSeparator(_:)

Interpose the separator between elements of self, then concatenate the result. For example:

["foo", "bar", "baz"].joinWithSeparator("-|-") // "foo-|-bar-|-baz"

Declaration

func joinWithSeparator(separator: String) -> String

Declared In

CollectionType, SequenceType

Where Index : BidirectionalIndexType

var last: Base.Generator.Element?

Declaration

var last: Base.Generator.Element? { get }

Declared In

CollectionType
func dropLast(_:)

Returns a subsequence containing all but the last n elements.

Requires: n >= 0 Complexity: O(n)

Declaration

func dropLast(n: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType
func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

func reverse() -> ReverseCollection<LazyCollection<Base>>

Declared In

CollectionType
func suffix(_:)

Returns a slice, up to maxLength in length, containing the final elements of s.

If maxLength exceeds s.count, the result contains all the elements of s.

Requires: maxLength >= 0 Complexity: O(maxLength)

Declaration

func suffix(maxLength: Int) -> LazyCollection<Slice<Base>>

Declared In

CollectionType

Where Index : BidirectionalIndexType, Elements.Index : BidirectionalIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

func reverse() -> LazyCollection<ReverseCollection<Base.Generator.Elements>>

Declared In

LazyCollectionType

Where Index : RandomAccessIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

func reverse() -> ReverseRandomAccessCollection<LazyCollection<Base>>

Declared In

CollectionType

Where Index : RandomAccessIndexType, Elements.Index : RandomAccessIndexType

func reverse()

Returns the elements of self in reverse order.

Complexity: O(1)

Declaration

func reverse() -> LazyCollection<ReverseRandomAccessCollection<Base.Generator.Elements>>

Declared In

LazyCollectionType

Where SubSequence == Self, Index : BidirectionalIndexType

mutating func popLast()

If !self.isEmpty, remove the last element and return it, otherwise return nil.

Complexity: O(1)

Declaration

mutating func popLast() -> Base.Generator.Element?

Declared In

CollectionType
mutating func removeLast()

Remove an element from the end.

Complexity: O(1) Requires: !self.isEmpty

Declaration

mutating func removeLast() -> Base.Generator.Element

Declared In

CollectionType
mutating func removeLast(_:)

Remove the last n elements.

Complexity: - O(1) if Index conforms to RandomAccessIndexType - O(n) otherwise Requires: n >= 0 && self.count >= n.

Declaration

mutating func removeLast(n: Int)

Declared In

CollectionType