Lecture 4 - slide 21 : 27

; R5RS syntactic abstraction:
(define-syntax my-delay 
  (syntax-rules ()
    ((my-delay expr)
     (lambda ()
        expr))))

; MzScheme syntactic abstraction:
(define-macro my-delay
  (lambda (expr)
    `(lambda () ,expr)))

(define (my-force promise)
  (promise))