; modified coin change (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 (sum xs) (apply + xs)) (define (f n) (sum (digits n 5))) (display (f 42)) (newline) (display (f 142)) (newline)