How to create lazy combinations

Question

My question is very simple, how do I make this code lazy:

/*
input: [
    [1, 2],
    [3, 4],
    [5, 6]
]

output: [
    [1, 3, 5],
    [1, 3, 6],
    [1, 4         


        

Answer 1

I found one possible solution, but I'll leave this answer not accepted for a while to see if someone knows a better one.

func combinations(options: [[T]]) -> LazySequence> {
    guard let head = options.first else {
        return AnySequence([].lazy.map({ [$0] })).lazy
    }

    if options.count == 1 {
        return AnySequence(head.lazy.map({ [$0] })).lazy
    }

    let tailCombinations = combinations(options: Array(options.dropFirst()))

    return AnySequence(head.lazy.flatMap({ option in
        return tailCombinations.lazy.map({ [option] + $0 })
    })).lazy
}

The solution was to use AnySequence instead of AnyCollection. I'm not sure why though, I'd still like to have the AnyCollection interface rather than AnySequence, since it provides me with a few more methods, like count.