; keypad errors
(define (digits n . args)
(let ((b (if (null? args) 10 (car args))))
(let loop ((n n) (d '()))
(if (zero? n) d
(loop (quotient n b)
(cons (modulo n b) d))))))
(define (remove x xs)
(let loop ((xs xs) (zs '()))
(cond ((null? xs) (reverse zs))
((equal? (car xs) x) (loop (cdr xs) zs))
(else (loop (cdr xs) (cons (car xs) zs))))))
(define (range . args)
(case (length args)
((1) (range 0 (car args) (if (negative? (car args)) -1 1)))
((2) (range (car args) (cadr args) (if (< (car args) (cadr args)) 1 -1)))
((3) (let ((le? (if (negative? (caddr args)) >= <=)))
(let loop ((x(car args)) (xs '()))
(if (le? (cadr args) x)
(reverse xs)
(loop (+ x (caddr args)) (cons x xs))))))
(else (error 'range "unrecognized arguments"))))
(define (match target keyed)
(let ((ts (digits target)) (ks (digits keyed)))
(if (equal? ts ks) #t
(let loop ((ds (range 10)))
(if (null? ds) #f
(if (equal? (remove (car ds) ts) ks) #t
(loop (cdr ds))))))))
(display (match 18684 164)) (newline)
(display (match 17674 164)) (newline)
(display (match 18684 165)) (newline)
(display (match 18684 18685)) (newline); your code goes here