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Before After in collection
public extension Collection where Iterator.Element: Equatable {
public func after(_ element: Iterator.Element) -> Iterator.Element? {
guard let idx = index(of: element), index(after: idx) < endIndex else { return nil }
let nextIdx = index(after: idx)
return self[nextIdx]
}
public func before(_ element: Iterator.Element) -> Iterator.Element? {
guard let idx = index(of: element), index(before: idx) >= startIndex else { return nil }
let previousIdx = index(idx, offsetBy: -1)
return self[previousIdx]
}
public func index(before idx: Index) -> Index {
return index(idx, offsetBy: -1)
}
}
