User blog comment:Vel!/BB(n) in FOST/@comment-1605058-20130709191627

For CountOnes, we can have variable C which starts as 0 and increases when 1 is written on blank and decreases when blank is written on 0. Otherwise, you can take number of steps S and count 1's on positions up to 2S at halting configuration. I'd love to see result in FOST!