Maybe you think the below program is trivial, but I adore named let's so much that I just cannot fathom that when people go functional they totally miss this beauty
(define (count tree) ;; s = total sum up to now ;; t = tree of the type (car = child . cdr = siblings) ;; cont is the continuation, (cont 10) will continue ;; the calculation with the sum=10 see how we initiate ;; with a continuation that evaluates returns it's argument (let loop ((s 0) (t tree) (cont (lambda (s) s))) (if (pair? t) (loop s (car t) (lambda (s) (loop s (cdr t) cont))) (cont (if (number? t) t 0))))
