From 716c16a4c409eaa18804c0e9c8f70982c99afb9e Mon Sep 17 00:00:00 2001
From: Yiyun Liu <liuyiyun@seas.upenn.edu>
Date: Thu, 5 Jun 2025 22:24:43 -0400
Subject: [PATCH] Update to treelist for the heap

---
 semantics.rkt | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/semantics.rkt b/semantics.rkt
index 4c0c68b..1300666 100644
--- a/semantics.rkt
+++ b/semantics.rkt
@@ -1,31 +1,27 @@
 #lang typed/racket
 (require "ast.rkt")
-
+(require racket/treelist)
 (: prelude CoreProgram)
 (define prelude
   '((define (I x) x) (define (K x y) x) (define (K1 x y) y) (define (S f g x) ((f x) (g x))) (define (compose f g x) (f (g x))) (define (twice f) ((compose f) f))))
 
 (struct State ([stack : Stack] [dump : Dump] [heap : Heap] [globals : Globals] [stats : Stats]))
-(define-type Addr Symbol)
+(define-type Addr Index)
 (define-type Stack (Listof Addr))
 (define-type Dump Null)
-(define-type Heap (Immutable-HashTable Addr Node))
+(define-type Heap (TreeListof Node))
 (define-type Node (∪ (List Addr Addr) CoreScDefn Integer))
 (define-type Globals (Immutable-HashTable Name Addr))
 (define-type Stats Nonnegative-Integer)
 
 (: empty-heap Heap)
 (define empty-heap
-  (make-immutable-hash))
+  (treelist))
 
 (: empty-globals Globals)
 (define empty-globals
   (make-immutable-hash))
 
-(: new-addr (-> Addr))
-(define (new-addr)
-  (gensym))
-
 (: empty-dump Dump)
 (define empty-dump '())
 
@@ -52,11 +48,11 @@
 
 (: allocate-node (-> Heap Node (Values Heap Addr)))
 (define (allocate-node heap node)
-  (let ([addr (new-addr)])
-    (values (hash-set heap addr node) addr)))
+  (let ([heap (treelist-add heap node)])
+    (values heap (treelist-length heap))))
 
 (: lookup-node (-> Heap Addr Node))
-(define lookup-node hash-ref)
+(define lookup-node treelist-ref)
 
 (: lookup-globals (-> Globals Name Addr))
 (define lookup-globals hash-ref)