Generic Structure

EnumeratedSequence

An enumeration of the elements of a sequence or collection.

Declaration

@frozen struct EnumeratedSequence<Base> where Base : Sequence

Overview

EnumeratedSequence is a sequence of pairs (n, x), where ns are consecutive Int values starting at zero, and xs are the elements of a base sequence.

To create an instance of EnumeratedSequence, call enumerated() on a sequence or collection. The following example enumerates the elements of an array.

var s = ["foo", "bar"].enumerated()
for (n, x) in s {
    print("\(n): \(x)")
}
// Prints "0: foo"
// Prints "1: bar"

Topics

Type Aliases

typealias EnumeratedSequence.Element

A type representing the sequence’s elements.

Beta

Instance Properties

var lazy: LazySequence<EnumeratedSequence<Base>>

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

var underestimatedCount: Int

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

Instance Methods

func allSatisfy(((offset: Int, element: Base.Element)) -> Bool) -> Bool

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

func compactMap<ElementOfResult>(((offset: Int, element: 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(where: ((offset: Int, element: Base.Element)) -> Bool) -> Bool

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

func drop(while: ((offset: Int, element: Base.Element)) -> Bool) -> DropWhileSequence<EnumeratedSequence<Base>>

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

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

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

func dropLast(Int) -> [(offset: Int, element: Base.Element)]

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

func elementsEqual<OtherSequence>(OtherSequence, by: ((offset: Int, element: 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<EnumeratedSequence<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(((offset: Int, element: Base.Element)) -> Bool) -> [(offset: Int, element: Base.Element)]

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

func first(where: ((offset: Int, element: Base.Element)) -> Bool) -> (offset: Int, element: Base.Element)?

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

func flatMap<SegmentOfResult>(((offset: Int, element: 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>(((offset: Int, element: 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(((offset: Int, element: Base.Element)) -> Void)

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

func lexicographicallyPrecedes<OtherSequence>(OtherSequence, by: ((offset: Int, element: Base.Element), (offset: Int, 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() -> EnumeratedSequence<Base>.Iterator

Returns an iterator over the elements of this sequence.

func map<T>(((offset: Int, element: Base.Element)) -> T) -> [T]

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

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

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

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

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

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

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

func prefix(while: ((offset: Int, element: Base.Element)) -> Bool) -> [(offset: Int, element: Base.Element)]

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

func reduce<Result>(Result, (Result, (offset: Int, element: 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, (offset: Int, element: Base.Element)) -> ()) -> Result

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

func reversed() -> [(offset: Int, element: Base.Element)]

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

func shuffled() -> [(offset: Int, element: Base.Element)]

Returns the elements of the sequence, shuffled.

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

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

func sorted(by: ((offset: Int, element: Base.Element), (offset: Int, element: Base.Element)) -> Bool) -> [(offset: Int, element: 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: ((offset: Int, element: Base.Element)) -> Bool) -> [ArraySlice<(offset: Int, element: 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 starts<PossiblePrefix>(with: PossiblePrefix, by: ((offset: Int, element: 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) -> [(offset: Int, element: Base.Element)]

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

func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<(offset: Int, element: 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.

Structures

struct EnumeratedSequence.Iterator

The iterator for EnumeratedSequence.

Relationships

Conforms To

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 FlattenSequence

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

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.

Beta Software

This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.

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