(define-syntax my-if
  (syntax-rules (then else)
    [(_ e1 then e2 else e3)
     (if e1 e2 e3)]
    [(_ e1 then e2)
     (if e1 e2)]))

(my-if (< 3 4) then 5 else 6)
(my-if (< 3 2) then 5 else 6)
(my-if (< 3 2) then 5)
(list (my-if (< 3 2) then 5))

(define-syntax ++
  (syntax-rules ()
    [(_ x)
     (begin (set! x (+ 1 x)) x)]))

(define a 5)
(++ a)
a
(define b (+ 3 (++ a)))
b
a

(define-syntax ++post
  (syntax-rules ()
    [(_ x)
     (let ([temp x])
       (++ x)
       temp)]))
(define b (+ 3 (++post a)))
b
a

(++ (* a 2))

(define-syntax my-and
  (syntax-rules ()
    [(_) #t]
    [(_ e) e]
    [(_ e1 e2 ...)
     (if e1
	 (my-and e2 ...)
	 #f)]))

(my-and)
(my-and 4)
(my-and 4 #f 6)
(my-and 4 5 6)
(expand '(my-and 4 5 6))

(define-syntax for
  (syntax-rules (:)
    [(for ((init ...) : test : update ...)
	  body ...)
     (begin init ...
	    (let for-loop ()
	      (if test
		  (begin body ...
			 update ...
			 (for-loop)))))]))

(for (((define i 0) (define j 1)) :
      (< i 12) :
      (++ i) (set! j (* 2 j)))
     (display i)
     (display "  ")
     (display j)
     (newline))