(define-struct s (args body f))

(define-syntax def
  (syntax-rules ()
    ((d name args body ...)
     (define name (make-s 'args
                          '(body ...)
                          #f)))))

(define (act an-s)
  (set-s-f! an-s
            (eval `(lambda ,(s-args an-s)
                     ,@(s-body an-s)))))

(define (app an-s . args)
  (apply (s-f an-s) args))

(define (my-f3 x) (* x x))

(def t1 (x) (* x x))
(act t1)
(printf "(app(t1 2) = ~a~n" (app t1 2))

(define (my-f2 x) (* x x))
(def t2 (x) (my-f2 x))
(act t2)
(printf "(my-f2 2) = ~a~n" (my-f2 2))
(printf "(app(t2 2) = ~a~n" (app t2 2))

(def t3 (x) (my-f3 x))
(act t3)
(printf "(my-f3 2) = ~a~n" (my-f3 2))
(printf "(app(t3 2) = ~a~n" (app t3 2))