(trace-define-syntax my-let
  (syntax-rules ()
    [(_ ((x v) ...) e1 e2 ...)
     ((lambda (x ...) e1 e2 ...)      v ...)])) 

'(define a 6)
'(my-let ([a 3][b (+ a 1)])
    (list a b))

(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 ++ ; (++ a) is like ++a in C or Java
  (syntax-rules ()
    [(_ x)
     (begin
       (set! x (+ 1 x))
       x)]))

(define-syntax ++-post ; (++-post a) is likw a++ in C or Java
  (syntax-rules ()
    [(_ x)
     (let ([result x])
       (set! x (+ 1 x))
       result)]))

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

(for (((define i 0)(define j 1)) : (< i 7) : (++ i) (set! j (* j 2)))
     (display (list i j)) (newline))

(trace-define-syntax my-and
  (syntax-rules ()
    [(_) #t]
    [(_ e) e]
    [(_ e1 e2 e3 ...) 
     (if e1
	 (my-and e2 e3 ...)
	 #f)]))