>>30
sure, I think all but the last would be amenable to letrec, for the last, it's not even clear what it means.
;; From SICP Section 4.16
(define (f x)
(define (even? n) (if (= n 0) #t (odd (- n 1))))
(define (odd? n) (if (= n 0) #t (even? (- n 1))))
<rest of body of f>)
(define (solve f y0 dt)
(define y (integral (delay dy) y0 dt))
(define dy (stream-map f y))
y)
(let ((a 1))
(define (f x)
(define b (+ a x))
(define a 5)
(+ a b))
(f 10))