Arc code to define places (i.e. getter-setters) with an example definition of 'push.

gistfile1.txt

; Copyright 2013 Ross Angle
;
; This code is released under the
; Perl Foundation's Artistic License 2.0.

; This code is an example for a forum post at
; <http://arclanguage.org/item?id=18051>.

(mac place (p)
  (w/uniq new-val
    `(make-place (fn () ,p) (fn (,new-val) (= ,p ,new-val)))))

(def make-place (getter setter)
  (annotate 'place (list getter setter)))

(def place-get (place)
  (rep.place.0))

(def place-set (place new-val)
  rep.place.1.new-val)

(defset place-get (place)
  (w/uniq g-place
    `((,g-place ,place)
      (place-get ,g-place)
      [place-set ,g-place _])))


(mac my-push (elem stack)
  `(fn-push ,elem (place ,stack)))

(def fn-push (elem stack)
  (zap [cons elem _] place-get.stack))