gistfile1.scm

  (class object%
    (init size)                ; initialization argument
  
    (define current-size size) ; field
  
    (super-new)                ; superclass initialization
  
    (define/public (get-size)
      current-size)
  
    (define/public (grow amt)
      (set! current-size (+ amt current-size)))
  
    (define/public (eat other-fish)
      (grow (send other-fish get-size))))