transcendental-lisp/lisp/random/array.lisp

(defmacro array (length)
  (let* ((this (gensym))
         (index-prefix (fuse this 'index))
         (indices (create-indices length))
         (index-bindings (map (lambda (i) (list (fuse index-prefix i))) indices)))

    `(let ,index-bindings
      (setq ,this
        (dlambda
          (:get (i)
            (eval (fuse ',index-prefix i)))

          (:set (i value)
            (if (< i ,length)
              (set (fuse ',index-prefix i) value)))

          (:length ()
            ,length)

          (t ()
            ((lambda (indices accumulator)
               (if (null? indices)
                 accumulator
                 (recur
                   (rest indices)
                   (cons
                     (list (first indices) (call ,this :get (first indices)))
                     accumulator))))
             (reverse ',indices)
             nil)))))))


(defun create-indices (length)
  (create-indices-tail (- length 1) ()))

(defun create-indices-tail (index accumulator)
  (if (< index 0)
    accumulator
    (recur (- index 1) (cons index accumulator))))