(define-syntax define-closures
  (syntax-rules ()
    [(_ ([var value] ...) [name body] ...)
     (define-values (name ...)
       (let ([var value] ...)
	       (letrec ([name body] ...)
	         (values name ...))))]))

(define-closures ([stack '()])
  [push (lambda (x)
	        (set! stack (cons x stack)))]
  [pop (lambda ()
	       (let ([x (car stack)])
	         (set! stack (cdr stack))
	         x))]
  [init (lambda ()
	        (set! stack '()))])