CPSの利用

(define (finder pred data report)
  (let loop ((data data) (r '()))
    (cond ((null? data)
           (report (reverse r) #f))
          ((pred (car data))
           (report (car data)
                   (lambda ()
                     (loop (cdr data) (cons (car data) r)))))
          (else (loop (cdr data) r)))))