program bell_numbers;
    print("First 15 and 50th Bell numbers:");
    b := bell_nums(50);
    loop for i in [1..15] with 50 do
        print(lpad(str i, 2) + ": " + str b(i));
    end loop;

    print;
    print("First 10 rows of the Bell triangle:");
    loop for row in bell_triangle(10) do
        print(+/[lpad(str n, 7) : n in row]);
    end loop;

    proc bell_nums(n);
        tri := bell_triangle(n);
        return [row(#row) : row in tri];
    end proc;

    proc bell_triangle(rows);
        tri := [[1]];
        loop for i in [2..rows] do
            row := tri(#tri);
            nextrow := [row(#row)];
            loop for n in row do
                nextrow with:= nextrow(#nextrow) + n;
            end loop;
            tri with:= nextrow;
        end loop;
        return tri;
    end proc;
end program;