Hi all, In Section 4.4. Iteration, the final example of vector-fold: Count the number of even numbers in vec. (vector-fold (lambda (index n counter) (if (even? n) (+ counter 1) counter)) 0 vec) but shouldn't it be (vector-fold (lambda (index counter n) Sincerely, Zhu Chongkai http://www.neilvandyke.org/mrmathematica/