function match_one(sequence key, object t)
    sequence res = {}
    if sequence(t)
    and length(key)==length(t) then
        for i=1 to length(key) do
            object ki = key[i], ti = t[i]
            if sequence(ki) and not string(ki) then
                sequence r2 = match_one(ki,ti)
                if r2={} then res = {} exit end if
                res &= r2
            else
                if ki=0 then
                    res = append(res,ti)
                else
                    if ki!=ti then res = {} exit end if
                end if
            end if
        end for
    end if
    return res
end function

/*global*/ function match_algebraic(sequence set, t)
    sequence s
    for i=1 to length(set) do
        s = match_one(set[i],t)
        if length(s) then exit end if
    end for
    return s
end function