Побитовые операции

(define (integer->byte a)
  (define (iter v k i)
    (begin
      (vector-set! v i (remainder k 2))
      (if (= i 7) v (iter v (quotient k 2) (+ i 1)))))
  (if (or (> a 255) (< a 0))
      'number-conversion-error
      (iter (vector 0 0 0 0 0 0 0 0) a 0)))

(define (byte->integer v)
  (define (iter i S)
    (if (= i 8) S (iter (+ i 1) (+ S (* (vector-ref v i) (expt 2 i))))))
  (iter 0 0))

(define (get-bit v i)
  (= (vector-ref v i) 1))

(define (set-bit a i)
  (begin
    (vector-set! a i 1)
    a))

(define (reset-bit a i)
  (begin
    (vector-set! a i 0)
    a))

(define (invert-bit a i)
  (begin
    (vector-set! a i (remainder (+ (vector-ref a i) 1) 2))
    a))