unison.js

// let rec reverse p1 p2 =
//     match p1 with
//     [] -> p2
//     | n :: p1’ -> reverse p1’ (n :: p2)

function reverse(p1, p2=[]) {
    if (!p1.length) {
        return p2;
    }
    const [n, ..._p1] = p1;
    return reverse(_p1, [n, ...p2]);
}