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//===----------------------------------------------------------*- swift -*-===//
//
// This source file is part of the Swift Argument Parser open source project
//
// Copyright (c) 2020 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
extension Sequence where Element: Hashable {
/// Returns an array with only the unique elements of this sequence, in the
/// order of the first occurrence of each unique element.
func uniquing() -> [Element] {
var seen = Set<Element>()
return self.filter { seen.insert($0).0 }
}
/// Returns an array, collapsing runs of consecutive equal elements into
/// the first element of each run.
///
/// [1, 2, 2, 2, 3, 3, 2, 2, 1, 1, 1].uniquingAdjacentElements()
/// // [1, 2, 3, 2, 1]
func uniquingAdjacentElements() -> [Element] {
var iterator = makeIterator()
guard let first = iterator.next()
else { return [] }
var result = [first]
while let element = iterator.next() {
if result.last != element {
result.append(element)
}
}
return result
}
}
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