void main()

{

    auto foo = Ways([Way([8,2,3,0]),Way([4,6,2]),Way([4,7,2,6])]);

​

    foo.remove_odds();

​

    assert(foo==Ways([Way([8, 2]), Way([4, 6, 2]), Way([4]), Way([0]), Way([2, 6])]));

}

​

struct Ways

{

    Way[] ways;

​

    void remove_odds()

    {

        Way[] new_ways;

​

        foreach (ref way;ways)

            foreach (point, void delegate(void delegate(Way way)) remove;way)

                if (point%2==1)

                    remove(delegate(Way way) {new_ways ~= way;});

​

        ways ~= new_ways;

    }

}

​

struct Way

{

    int[] points;

​

    auto opApply(int delegate(int, void delegate(void delegate(Way way))) work)

    {

        size_t[] remove;

        void delegate(Way) add_new_way;

​

        foreach (index,point;points)

            if (auto result=work(point,(void delegate(Way) anw){remove~=index; add_new_way=anw;}))

                return result;

​

        import std.algorithm.sorting: sort;

        foreach (index;remove.sort!("a>b"))

        {

            add_new_way(Way(points[index+1..$]));

            points = points[0..index];

        }

​

        return 0;

    }

}

​