Is it possible to create a cartesian product function with parameter packs?

[vanvoorden (Rick van Voorden)]

There might be some clues in here how this might be possible:

Algorithms package: product(_:_) limited to two product terms only, for homogeneous element type, there should be one for any number of product terms?

Almost got it (Godbolt): struct ProductSequence<each Base: Sequence> { let base: (repeat each Base) init(_ base: repeat each Base) { self.base = (repeat each base) } } extension ProductSequence: Sequence { typealias Element = (repeat (each Base).Element) struct Iterator: IteratorProtocol { let base: (repeat each Base) var iterator: (repeat (each Base).Iterator) var element: Element? var started = false var complete = false …