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ba208cd672
// Renamed from `ZipGenerator2`.
struct Zip2Generator<Generator1 : GeneratorType, Generator2 : GeneratorType> { ... }
// Renamed from `Zip2`.
struct Zip2Sequence<Sequence1 : SequenceType, Sequence2 : SequenceType> { ... }
Part of rdar://21429126
Swift SVN r29636
98 lines
3.3 KiB
Swift
98 lines
3.3 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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/// A sequence of pairs built out of two underlying sequences, where
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/// the elements of the `i`th pair are the `i`th elements of each
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/// underlying sequence.
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public func zip<Sequence1 : SequenceType, Sequence2 : SequenceType>(
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sequence1: Sequence1, _ sequence2: Sequence2
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) -> Zip2Sequence<Sequence1, Sequence2> {
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return Zip2Sequence(sequence1, sequence2)
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}
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/// A generator for `Zip2Sequence`.
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public struct Zip2Generator<
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Generator1 : GeneratorType, Generator2 : GeneratorType
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> : GeneratorType {
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/// The type of element returned by `next()`.
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public typealias Element = (Generator1.Element, Generator2.Element)
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/// Construct around a pair of underlying generators.
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public init(_ generator1: Generator1, _ generator2: Generator2) {
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_baseStreams = (generator1, generator2)
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}
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/// Advance to the next element and return it, or `nil` if no next
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/// element exists.
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///
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/// - Requires: `next()` has not been applied to a copy of `self`
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/// since the copy was made, and no preceding call to `self.next()`
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/// has returned `nil`.
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public mutating func next() -> Element? {
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// The next() function needs to track if it has reached the end. If we
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// didn't, and the first sequence is shorter than the second, then, when we
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// have already exhausted the second sequence, on every subsequent call to
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// next() we would consume and discard one additional element from the
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// first sequence, even though next() return nil.
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if _reachedEnd {
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return nil
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}
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guard let e0 = _baseStreams.0.next() else {
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_reachedEnd = true
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return nil
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}
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guard let e1 = _baseStreams.1.next() else {
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_reachedEnd = true
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return nil
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}
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return .Some((e0, e1))
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}
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internal var _baseStreams: (Generator1, Generator2)
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internal var _reachedEnd: Bool = false
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}
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/// A sequence of pairs built out of two underlying sequences, where
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/// the elements of the `i`th pair are the `i`th elements of each
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/// underlying sequence.
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public struct Zip2Sequence<Sequence1 : SequenceType, Sequence2 : SequenceType>
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: SequenceType {
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public typealias Stream1 = Sequence1.Generator
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public typealias Stream2 = Sequence2.Generator
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/// A type whose instances can produce the elements of this
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/// sequence, in order.
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public typealias Generator = Zip2Generator<Stream1, Stream2>
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/// Construct an instance that makes pairs of elements from `sequence1` and
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/// `sequence2`.
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public init(_ sequence1: Sequence1, _ sequence2: Sequence2) {
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_sequences = (sequence1, sequence2)
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}
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/// Return a *generator* over the elements of this *sequence*.
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///
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/// - Complexity: O(1).
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public func generate() -> Generator {
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return Generator(
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_sequences.0.generate(),
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_sequences.1.generate())
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}
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internal let _sequences: (Sequence1, Sequence2)
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}
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