Variadic Zip Function
Swift 4.1, Xcode 9.4
Я недавно использовал нативную zip(_:_:) от Apple, и я столкнулся с ситуацией, когда мне нужно zip более двух последовательностей.
Итак, я искал и нашел объявление zip(_:_:) на странице Swift GitHub .Я взял эту информацию и смог перегрузить zip(_:_:), чтобы принять четыре параметра, zip(_:_:_:_:).Я знаю, что могу кропотливо перегрузить zip для поддержки любого количества аргументов, которые я выбрал по одному за раз, но это негибко, отнимает много времени, и я чувствую, что вариант с вариацией будет гораздо лучшим выбором.
Вопрос:
Как заставить собственную функцию zip принимать переменный параметр, который может содержать любое количество входов последовательности.
Родной Apple zip(_:_:) Функция
/// Creates a sequence of pairs built out of two underlying sequences.
///
/// In the `Zip2Sequence` instance returned by this function, the elements of
/// the *i*th pair are the *i*th elements of each underlying sequence. The
/// following example uses the `zip(_:_:)` function to iterate over an array
/// of strings and a countable range at the same time:
///
/// let words = ["one", "two", "three", "four"]
/// let numbers = 1...4
///
/// for (word, number) in zip(words, numbers) {
/// print("\(word): \(number)")
/// }
/// // Prints "one: 1"
/// // Prints "two: 2
/// // Prints "three: 3"
/// // Prints "four: 4"
///
/// If the two sequences passed to `zip(_:_:)` are different lengths, the
/// resulting sequence is the same length as the shorter sequence. In this
/// example, the resulting array is the same length as `words`:
///
/// let naturalNumbers = 1...Int.max
/// let zipped = Array(zip(words, naturalNumbers))
/// // zipped == [("one", 1), ("two", 2), ("three", 3), ("four", 4)]
///
/// - Parameters:
/// - sequence1: The first sequence or collection to zip.
/// - sequence2: The second sequence or collection to zip.
/// - Returns: A sequence of tuple pairs, where the elements of each pair are
/// corresponding elements of `sequence1` and `sequence2`.
@inlinable // FIXME(sil-serialize-all)
public func zip<Sequence1, Sequence2>(
_ sequence1: Sequence1, _ sequence2: Sequence2
) -> Zip2Sequence<Sequence1, Sequence2> {
return Zip2Sequence(_sequence1: sequence1, _sequence2: sequence2)
}
/// A sequence of pairs built out of two underlying sequences.
///
/// In a `Zip2Sequence` instance, the elements of the *i*th pair are the *i*th
/// elements of each underlying sequence. To create a `Zip2Sequence` instance,
/// use the `zip(_:_:)` function.
///
/// The following example uses the `zip(_:_:)` function to iterate over an
/// array of strings and a countable range at the same time:
///
/// let words = ["one", "two", "three", "four"]
/// let numbers = 1...4
///
/// for (word, number) in zip(words, numbers) {
/// print("\(word): \(number)")
/// }
/// // Prints "one: 1"
/// // Prints "two: 2
/// // Prints "three: 3"
/// // Prints "four: 4"
@_fixed_layout // FIXME(sil-serialize-all)
public struct Zip2Sequence<Sequence1 : Sequence, Sequence2 : Sequence> {
@usableFromInline // FIXME(sil-serialize-all)
internal let _sequence1: Sequence1
@usableFromInline // FIXME(sil-serialize-all)
internal let _sequence2: Sequence2
@available(*, deprecated, renamed: "Sequence1.Iterator")
public typealias Stream1 = Sequence1.Iterator
@available(*, deprecated, renamed: "Sequence2.Iterator")
public typealias Stream2 = Sequence2.Iterator
/// Creates an instance that makes pairs of elements from `sequence1` and
/// `sequence2`.
@inlinable // FIXME(sil-serialize-all)
public // @testable
init(_sequence1 sequence1: Sequence1, _sequence2 sequence2: Sequence2) {
(_sequence1, _sequence2) = (sequence1, sequence2)
}
}
extension Zip2Sequence {
/// An iterator for `Zip2Sequence`.
@_fixed_layout // FIXME(sil-serialize-all)
public struct Iterator {
@usableFromInline // FIXME(sil-serialize-all)
internal var _baseStream1: Sequence1.Iterator
@usableFromInline // FIXME(sil-serialize-all)
internal var _baseStream2: Sequence2.Iterator
@usableFromInline // FIXME(sil-serialize-all)
internal var _reachedEnd: Bool = false
/// Creates an instance around a pair of underlying iterators.
@inlinable // FIXME(sil-serialize-all)
internal init(
_ iterator1: Sequence1.Iterator,
_ iterator2: Sequence2.Iterator
) {
(_baseStream1, _baseStream2) = (iterator1, iterator2)
}
}
}
extension Zip2Sequence.Iterator: IteratorProtocol {
/// The type of element returned by `next()`.
public typealias Element = (Sequence1.Element, Sequence2.Element)
/// Advances to the next element and returns it, or `nil` if no next element
/// exists.
///
/// Once `nil` has been returned, all subsequent calls return `nil`.
@inlinable // FIXME(sil-serialize-all)
public mutating func next() -> Element? {
// The next() function needs to track if it has reached the end. If we
// didn't, and the first sequence is longer than the second, then when we
// have already exhausted the second sequence, on every subsequent call to
// next() we would consume and discard one additional element from the
// first sequence, even though next() had already returned nil.
if _reachedEnd {
return nil
}
guard let element1 = _baseStream1.next(),
let element2 = _baseStream2.next() else {
_reachedEnd = true
return nil
}
return (element1, element2)
}
}
extension Zip2Sequence: Sequence {
public typealias Element = (Sequence1.Element, Sequence2.Element)
/// Returns an iterator over the elements of this sequence.
@inlinable // FIXME(sil-serialize-all)
public func makeIterator() -> Iterator {
return Iterator(
_sequence1.makeIterator(),
_sequence2.makeIterator())
}
}
// @available(*, deprecated, renamed: "Zip2Sequence.Iterator")
public typealias Zip2Iterator<T, U> = Zip2Sequence<T, U>.Iterator where T: Sequence, U: Sequence
zip(_:_:_:_:) Перегрузка функции (моя реализация)
/// Creates a sequence of pairs built out of four underlying sequences.
///
/// In the `Zip4Sequence` instance returned by this function, the elements of
/// the *i*th pair are the *i*th elements of each underlying sequence. The
/// following example uses the `zip(_:_:_:_:)` function to iterate over an array
/// of strings, an array of bolean values, an array of integer values, and a countable range, at the same time:
///
/// let evens = [false, true, false, true)
/// let squares = [1, 4, 9, 16]
/// let words = ["one", "two", "three", "four"]
/// let numbers = 1...4
///
/// for (word, number, even, square) in zip(words, numbers, evens, squares) {
/// print("\(word): \(number) --> \(number) is \(even ? "even" : "odd") and \(number)² = \(square)")
/// }
/// // Prints "one: 1 --> 1 is odd and 1² = 1"
/// // Prints "two: 2 --> 2 is even and 2² = 4"
/// // Prints "three: 3 --> 3 is odd and 3² = 9"
/// // Prints "four: 4 --> 4 is even and 4² = 16"
///
/// If the four sequences passed to `zip(_:_:_:_:)` are different lengths, the
/// resulting sequence is the same length as the shorter sequence. In this
/// example, the resulting array is the same length as `words`, `evens`, `and `squares`:
///
/// let naturalNumbers = 1...Int.max
/// let zipped = Array(zip(words, naturalNumbers, evens, squares))
/// // zipped == [("one", 1, false, 1), ("two", 2, true, 4), ("three", 3, false, 9), ("four", 4, true, 16)]
///
/// - Parameters:
/// - sequence1: The first sequence or collection to zip.
/// - sequence2: The second sequence or collection to zip.
/// - sequence3: The third sequence or collection to zip.
/// - sequence4: The fourth sequence or collection to zip.
/// - Returns: A sequence of tuple pairs, where the elements of each pair are
/// corresponding elements of `sequence1`, `sequence2`, `sequence3`, and `sequence3`.
public func zip<Sequence1, Sequence2, Sequence3, Sequence4>(
_ sequence1: Sequence1, _ sequence2: Sequence2, _ sequence3: Sequence3, _ sequence4: Sequence4
) -> Zip4Sequence<Sequence1, Sequence2, Sequence3, Sequence4> {
return Zip4Sequence(_sequence1: sequence1, _sequence2: sequence2, _sequence3: sequence3, _sequence4: sequence4)
}
/// A sequence of pairs built out of four underlying sequences.
///
/// In a `Zip4Sequence` instance, the elements of the *i*th pair are the *i*th
/// elements of each underlying sequence. To create a `Zip4Sequence` instance,
/// use the `zip(_:_:_:_:)` function.
///
/// The following example uses the `zip(_:_:_:_:)` function to iterate over an array
/// of strings, an array of bolean values, an array of integer values, and a countable range, at the same time:
////
/// let evens = [false, true, false, true)
/// let squares = [1, 4, 9, 16]
/// let words = ["one", "two", "three", "four"]
/// let numbers = 1...4
///
/// for (word, number, even, square) in zip(words, numbers, evens, squares) {
/// print("\(word): \(number) --> \(number) is \(even ? "even" : "odd") and \(number)² = \(square)")
/// }
/// // Prints "one: 1 --> 1 is odd and 1² = 1"
/// // Prints "two: 2 --> 2 is even and 2² = 4"
/// // Prints "three: 3 --> 3 is odd and 3² = 9"
/// // Prints "four: 4 --> 4 is even and 4² = 16"
@_fixed_layout // FIXME(sil-serialize-all)
public struct Zip4Sequence<Sequence1 : Sequence, Sequence2 : Sequence, Sequence3 : Sequence, Sequence4 : Sequence> {
internal let _sequence1: Sequence1
internal let _sequence2: Sequence2
internal let _sequence3: Sequence3
internal let _sequence4: Sequence4
@available(*, deprecated, renamed: "Sequence1.Iterator")
public typealias Stream1 = Sequence1.Iterator
@available(*, deprecated, renamed: "Sequence2.Iterator")
public typealias Stream2 = Sequence2.Iterator
@available(*, deprecated, renamed: "Sequence3.Iterator")
public typealias Stream3 = Sequence3.Iterator
@available(*, deprecated, renamed: "Sequence4.Iterator")
public typealias Stream4 = Sequence4.Iterator
/// Creates an instance that makes pairs of elements from `sequence1` and
/// `sequence2`.
public // @testable
init(_sequence1 sequence1: Sequence1, _sequence2 sequence2: Sequence2, _sequence3 sequence3: Sequence3, _sequence4 sequence4: Sequence4) {
(_sequence1, _sequence2, _sequence3, _sequence4) = (sequence1, sequence2, sequence3, sequence4)
}
}
extension Zip4Sequence {
/// An iterator for `Zip4Sequence`.
@_fixed_layout // FIXME(sil-serialize-all)
public struct Iterator {
internal var _baseStream1: Sequence1.Iterator
internal var _baseStream2: Sequence2.Iterator
internal var _baseStream3: Sequence3.Iterator
internal var _baseStream4: Sequence4.Iterator
internal var _reachedEnd: Bool = false
/// Creates an instance around a set of 4 underlying iterators.
internal init(
_ iterator1: Sequence1.Iterator,
_ iterator2: Sequence2.Iterator,
_ iterator3: Sequence3.Iterator,
_ iterator4: Sequence4.Iterator
) {
(_baseStream1, _baseStream2, _baseStream3, _baseStream4) = (iterator1, iterator2, iterator3, iterator4)
}
}
}
extension Zip4Sequence.Iterator: IteratorProtocol {
/// The type of element returned by `next()`.
public typealias Element = (Sequence1.Element, Sequence2.Element, Sequence3.Element, Sequence4.Element)
/// Advances to the next element and returns it, or `nil` if no next element
/// exists.
///
/// Once `nil` has been returned, all subsequent calls return `nil`.
public mutating func next() -> Element? {
// The next() function needs to track if it has reached the end. If we
// didn't, and the first sequence is longer than the second, third, and
// fourth, then when we have already exhausted the second, third, and
// fourth sequence, on every subsequent call to next() we would consume
// and discard one additional element from the first sequence, even
// though next() had already returned nil.
if _reachedEnd {
return nil
}
guard let element1 = _baseStream1.next(),
let element2 = _baseStream2.next(),
let element3 = _baseStream3.next(),
let element4 = _baseStream4.next()
else {
_reachedEnd = true
return nil
}
return (element1, element2, element3, element4)
}
}
extension Zip4Sequence: Sequence {
public typealias Element = (Sequence1.Element, Sequence2.Element, Sequence3.Element, Sequence4.Element)
/// Returns an iterator over the elements of this sequence.
public func makeIterator() -> Iterator {
return Iterator(
_sequence1.makeIterator(),
_sequence2.makeIterator(),
_sequence3.makeIterator(),
_sequence4.makeIterator())
}
}
@available(*, deprecated, renamed: "Zip4Sequence.Iterator")
public typealias Zip4Iterator<T, U, V, W> = Zip4Sequence<T, U, V, W>.Iterator where T: Sequence, U: Sequence, V: Sequence, W: Sequence
Предупреждение: Эта перегрузка предназначена только для фиксированного числа входов, тогда как в идеале я ищу функцию zip, которая принимает беспорядочное количество входов AnySequence.
Просто дляеще раз, я хочу создать функцию zip(_: AnySequence...), которую я могу использовать для архивирования любого числа последовательностей с помощью параметра variadic .
Спасибо всем заранее за всю вашу помощь, я действительно ценю это!