Fans of the zip(_:_:) function may find that the opposite operation, while easy to implement using reduce(into:), is arguably not as readable. The unzip(_:) function helps with that.

unzip.swift

/// Creates a pair of sequences built out of an underlying sequence of pairs, i.e. the inverse of `zip(_:_:)`.
///
///     let wordsAndNumbers = [
///         ("one", 1),
///         ("two", 2),
///         ("three", 3),
///         ("four", 4)
///     ]
///
///     let unzipped = unzip(wordsAndNumbers)
///     // unzipped == (["one", "two", "three", "four"], [1, 2, 3, 4])
///
/// - Parameters:
///   - sequence: The sequence or collection to unzip.
/// - Returns: A tuple pair of sequences, where the elements of each sequence are the first and second elements, respectively, of the corresponding elements of `sequence`.
func unzip<E1, E2, S: Sequence>(_ sequence: S) -> ([E1], [E2]) where S.Element == (E1, E2) {
    sequence.reduce(into: ([E1](), [E2]())) {
        $0.0.append($1.0)
        $0.1.append($1.1)
    }
}