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df2307e035
* Concretize dropFirst/Last/sufix/prefix from Sequence Remove split customization point Eliminate SubSequence from Sequence protocol Collapse LazyCollection Collapse LazyMapCollection Eliminate _SequenceWrapper Collapse LazyFilterCollection Collapse LazyDrop/PrefixWhileCollection Fix tests, ABI stability update Collapse FlattenSequence * Add entries to source/ABI compatible expected results. * Update tests to avoid pre-10.14 objc runtime bug * Expunge _preprocessingPass
52 lines
1.9 KiB
Swift
52 lines
1.9 KiB
Swift
//===--- FlatMap.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 - 2017 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 https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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extension LazySequenceProtocol {
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/// Returns the concatenated results of mapping the given transformation over
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/// this sequence.
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///
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/// Use this method to receive a single-level sequence when your
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/// transformation produces a sequence or collection for each element.
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/// Calling `flatMap(_:)` on a sequence `s` is equivalent to calling
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/// `s.map(transform).joined()`.
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///
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/// - Complexity: O(1)
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@inlinable // lazy-performance
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public func flatMap<SegmentOfResult>(
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_ transform: @escaping (Elements.Element) -> SegmentOfResult
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) -> LazySequence<
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FlattenSequence<LazyMapSequence<Elements, SegmentOfResult>>> {
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return self.map(transform).joined()
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}
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/// Returns the non-`nil` results of mapping the given transformation over
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/// this sequence.
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///
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/// Use this method to receive a sequence of non-optional values when your
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/// transformation produces an optional value.
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///
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/// - Parameter transform: A closure that accepts an element of this sequence
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/// as its argument and returns an optional value.
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///
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/// - Complexity: O(1)
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@inlinable // lazy-performance
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public func compactMap<ElementOfResult>(
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_ transform: @escaping (Elements.Element) -> ElementOfResult?
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) -> LazyMapSequence<
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LazyFilterSequence<
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LazyMapSequence<Elements, ElementOfResult?>>,
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ElementOfResult
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> {
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return self.map(transform).filter { $0 != nil }.map { $0! }
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}
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}
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