From 3e24991be80d799ceda5a911184162e50994da95 Mon Sep 17 00:00:00 2001
From: Mike Cifelli <michael.cifelli@gmail.com>
Date: Sun, 28 Jan 2018 09:55:23 -0500
Subject: [PATCH] Create a direct access array

---
 lisp/random/array.lisp | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/lisp/random/array.lisp b/lisp/random/array.lisp
index b94a19e..f68942d 100644
--- a/lisp/random/array.lisp
+++ b/lisp/random/array.lisp
@@ -1,11 +1,37 @@
-(defmacro array (size)
-  `(let ,(map (lambda (x) (list (fuse 'index x))) (create-indices size))
-    (dlambda
-      (:get (i) (eval (fuse 'index i)))
-      (:set (i value) (set (fuse 'index i) value)))))
+(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)))
 
-(defun create-indices (size)
-  (create-indices-tail (- size 1) ()))
+    `(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)