void
test_string(text &g, v, l)
{
    integer n;

    n = prefix(v, l);
    if (~g < n) {
        g = cut(l, 0, n);
    }
}

longest(text u, v)
{
    record r;
    text g, l, s;

    while (~u) {
        r[u] = 0;
        u = delete(u, 0);
    }
    while (~v) {
        if (rsk_lower(r, v, l)) {
            test_string(g, v, l);
        }
        if (rsk_upper(r, v, l)) {
            test_string(g, v, l);
        }
        v = delete(v, 0);
    }

    g;
}