(define (map fn lst)
  (if (null? lst)
      '()
      (cons (fn (car lst))
	    (map fn (cdr lst)))))

(define (vector-map fn vec)
  (define (loop newvec n)
    (if (< n 0)
	newvec
	(begin (vector-set! newvec n (fn (vector-ref vec n)))
	       (loop newvec (- n 1)))))
  (loop (make-vector (vector-length vec)) (- (vector-length vec) 1)))

(define (vector-cons value vec)
  (define (loop newvec n)
    (if (= n 0)
	(begin (vector-set! newvec n value)
	       newvec)
	(begin (vector-set! newvec n (vector-ref vec (- n 1)))
	       (loop newvec (- n 1)))))
  (loop (make-vector (+ (vector-length vec) 1)) (vector-length vec)))

(define (shuffle1 lst)
  (define (loop in out n)
    (if (= n 0)
	(cons (car in) (shuffle1 (append (cdr in) out)))
	(loop (cdr in) (cons (car in) out) (- n 1))))
  (if (null? lst)
      '()
      (loop lst '() (random (length lst)))))

(define (shuffle2! lst)
  (if (null? lst)
      '()
      (let ((index (random (length lst))))
	(let ((pair ((repeated cdr index) lst))
	      (temp (car lst)))
	  (set-car! lst (car pair))
	  (set-car! pair temp)
	  (shuffle2! (cdr lst))
	  lst))))

(define (shuffle3! vec)
  (define (loop n)
    (if (= n 0)
	vec
	(let ((index (random n))
	      (temp (vector-ref vec (- n 1))))
	  (vector-set! vec (- n 1) (vector-ref vec index))
	  (vector-set! vec index temp)
	  (loop (- n 1)))))
  (loop (vector-length vec)))