Non-continuous subsequences

func non_continuous(min, max, subseq=[], has_gap=false) {
 
    static current = []
 
    for i in (min .. max) {
        current.push(i)
        has_gap && subseq.append([current...])
        i < max && non_continuous(i.inc, max, subseq, has_gap)
        current.pop
        has_gap = current.len
    }
 
    return subseq
}
 
say non_continuous(1, 3)
say non_continuous(1, 4)
say non_continuous("a", "d")

Output:

[[1, 3]]
[[1, 2, 4], [1, 3], [1, 3, 4], [1, 4], [2, 4]]
[["a", "b", "d"], ["a", "c"], ["a", "c", "d"], ["a", "d"], ["b", "d"]]