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

(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 (+ 1 x))
            x))))

(define-syntax ++-post
  (syntax-rules ()
    ((_ x)
     (let ([old-value x])
       (set! x (+ 1 x))
       old-value))))

(define-syntax for
  (syntax-rules (:)
    ((_ ((init ...) : test : update ...) body ...)
     (begin
       init ...
       (let loop ()
         (if test
             (begin
               body ...
               update ...
               (loop))))))
    ((_ (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)
    ((_ exp exp2 exp3 ...) 
     (if exp
         (my-and exp2 exp3 ...)
         #f))
    ))