Return the unique elements of a sequence while maintaining the order of the input sequence

Sequence+unique.swift

public extension Sequence where Element: Equatable {
	/// Return the unique elements in the array using Equatable as the predicate
	var unique: [Element] {
		return self.reduce(into: []) { uniqueElements, element in
			if !uniqueElements.contains(element) {
				uniqueElements.append(element)
			}
		}
	}
}