Progress slowing down

A couple of hours and only managed to get 3 exercises done cleanly today... Bad day perhaps? Getting easily distracted. Solution to 2.35 just because it's really cool:

count-leaves as an accumulation:

(define (count-leaves t)
   (accumulate + 0 (map (lambda (x)
                          (if (pair? x)
                              (count-leaves x)
                              1))
                        t)))

And for reference, accumulate is:

(define (accumulate op initial sequence)
  (if (null? sequence)
      initial
      (op (car sequence)
          (accumulate op initial (cdr sequence)))))

Also an alternative map function from one of the other exercises:

(define (map p sequence)
    (accumulate (lambda (x y) (cons (p x) y)) nil sequence))

Mind-bending, but fun stuff.

Edit: well, I was going to sleep, but the next exercise looked interesting too, so I figured it out much quicker(finally getting the hang of using lambda?!)

sicp exercise 3.36:

(define (accumulate-n op init seqs)
  (if (null? (car seqs))
      null
      (cons (accumulate op init (accumulate (lambda (x y) (cons (car x) y)) null seqs))
            (accumulate-n op init (accumulate (lambda (x y) (cons (cdr x) y)) null seqs)))))