Swift unique functionality for Sequences / Collections, option to keep the first or the last occurrence of the duplicated element.

UniqueSequence.swift

public extension Sequence where Element : Hashable {
	
	/// Returns an array containing the unique elements from the sequence.
	///
	/// - Parameter keepLast: A boolean value indicating whether to keep the last occurrence of each duplicated element.
	/// If `true`, the last occurrence is kept. If `false`, the first occurrence is kept. The default value is `false`.
	/// - Returns: An array containing the unique elements from the sequence based on the `keepLast` behavior.
	/// - Complexity: O(n), where `n` is the length of the sequence.
	func unique(keepLast: Bool = false) -> [Element] {
		guard !keepLast else { return reversed().unique(keepLast: false).reversed() }
		var seen = Set<Element>()
		return filter { seen.insert($0).inserted }
	}
}