z.scm

(define (read-until p reader)
  (let loop ((result '()))
    (let1 e (reader)
      (cond [(p e) (reverse result)]
            [else (loop (cons e result))]))))

(define (read-sentence)
  (display ":-) ")
  (read-until (cut eq? <> '@) read)) ;;gaucheは'.を受け付けない