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

(define-syntax ++
  (syntax-rules ()
    [(_ x) (begin (set! x (add1 x))
		  x)]))

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

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

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

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