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

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

(define-syntax ++-post
  (syntax-rules ()
    [(_ x)
     (let ([temp x])
       (set! x (add1 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 ()
    [(_) #t]
    [(_ exp) exp]
    [(_ exp1 exp2 ...)
     (if exp1
	 (my-and exp2 ...)
	 #f)]))