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23 lines
777 B
Swift
23 lines
777 B
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 - 2023 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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public extension Collection {
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/// If the collection contains a single element, return it, otherwise `nil`.
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var only: Element? {
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if !isEmpty && index(after: startIndex) == endIndex {
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return self.first!
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} else {
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return nil
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}
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}
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}
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