diff --git a/evildoer/random.rkt b/evildoer/random.rkt
index b6443e5..88b002c 100644
--- a/evildoer/random.rkt
+++ b/evildoer/random.rkt
@@ -1,5 +1,5 @@
 #lang racket
-(provide random-expr random-well-defined-expr)
+(provide random-expr random-well-defined-expr random-input)
 (require "parse.rkt")
 
 ;; Randomly generate an expression
@@ -10,6 +10,9 @@
 (define (random-well-defined-expr)
   (parse (contract-random-generate expr-good/c)))
 
+(define (random-input)
+  (contract-random-generate string?))
+
 (define op0/c
   (one-of/c 'read-byte 'peek-byte 'void))
 
diff --git a/extort/random.rkt b/extort/random.rkt
index b6443e5..88b002c 100644
--- a/extort/random.rkt
+++ b/extort/random.rkt
@@ -1,5 +1,5 @@
 #lang racket
-(provide random-expr random-well-defined-expr)
+(provide random-expr random-well-defined-expr random-input)
 (require "parse.rkt")
 
 ;; Randomly generate an expression
@@ -10,6 +10,9 @@
 (define (random-well-defined-expr)
   (parse (contract-random-generate expr-good/c)))
 
+(define (random-input)
+  (contract-random-generate string?))
+
 (define op0/c
   (one-of/c 'read-byte 'peek-byte 'void))
 
diff --git a/hustle/heap.rkt b/hustle/heap.rkt
index 0f7eb34..4d477a3 100644
--- a/hustle/heap.rkt
+++ b/hustle/heap.rkt
@@ -1,15 +1,18 @@
 #lang racket
-(provide alloc-box alloc-cons heap-ref heap-set)
+(provide alloc-box alloc-cons heap-ref heap-set box-ptr cons-ptr)
+
+(struct box-ptr (i))
+(struct cons-ptr (i))
 
 ;; Value* Heap -> Answer*
 (define (alloc-box v h)
   (cons (cons v h)
-        (list 'box (length h))))
+        (box-ptr (length h))))
 
 ;; Value* Value* Heap -> Answer*
 (define (alloc-cons v1 v2 h)
   (cons (cons v2 (cons v1 h))
-        (list 'cons (length h))))
+        (cons-ptr (length h))))
 
 ;; Heap Address -> Value*
 (define (heap-ref h a)
diff --git a/hustle/interp-heap.rkt b/hustle/interp-heap.rkt
index 0256171..6909013 100644
--- a/hustle/interp-heap.rkt
+++ b/hustle/interp-heap.rkt
@@ -16,14 +16,16 @@
 ;; | Eof
 ;; | Void
 ;; | '()
-;; | (list 'box  Address)
-;; | (list 'cons Address)
+;; | (box-ptr  Address)
+;; | (cons-ptr Address)
+
+;; type Address = Natural
 
 ;; type Heap = (Listof Value*)
 ;; type REnv = (Listof (List Id Value*))
 
 ;; Expr -> Answer
-(define (interp e)  
+(define (interp e)
   (unload (interp-env-heap e '() '())))
 
 ;; Expr REnv Heap -> Answer*
@@ -55,7 +57,7 @@
         (if v
             (interp-env-heap e1 r h)
             (interp-env-heap e2 r h))])]
-    [(Begin e1 e2)     
+    [(Begin e1 e2)
      (match (interp-env-heap e1 r h)
        ['err 'err]
        [(cons h _) (interp-env-heap e2 r h)])]
diff --git a/hustle/interp-prims-heap.rkt b/hustle/interp-prims-heap.rkt
index 53cbd4f..9ceaaa1 100644
--- a/hustle/interp-prims-heap.rkt
+++ b/hustle/interp-prims-heap.rkt
@@ -14,9 +14,9 @@
     [(list 'eof-object? v)                (cons h (eof-object? v))]
     [(list 'write-byte (? byte?))         (cons h (write-byte v))]
     [(list 'box v)                        (alloc-box v h)]
-    [(list 'unbox (list 'box i))          (cons h (heap-ref h i))]
-    [(list 'car   (list 'cons i))         (cons h (heap-ref h i))]
-    [(list 'cdr   (list 'cons i))         (cons h (heap-ref h (add1 i)))]
+    [(list 'unbox (box-ptr i))            (cons h (heap-ref h i))]
+    [(list 'car   (cons-ptr i))           (cons h (heap-ref h i))]
+    [(list 'cdr   (cons-ptr i))           (cons h (heap-ref h (add1 i)))]
     [(list 'empty? v)                     (cons h (empty? v))]
     [_                                    'err]))
 
@@ -26,7 +26,7 @@
     [(list '+ (? integer? i1) (? integer? i2)) (cons h (+ i1 i2))]
     [(list '- (? integer? i1) (? integer? i2)) (cons h (- i1 i2))]
     [(list '< (? integer? i1) (? integer? i2)) (cons h (< i1 i2))]
-    [(list '= (? integer? i1) (? integer? i2)) (cons h (= i1 i2))]    
+    [(list '= (? integer? i1) (? integer? i2)) (cons h (= i1 i2))]
     [(list 'eq? v1 v2)
      (match (list v1 v2)
        [(list (list t1 a1)  (list t2 a2)) (cons h (and (eq? t1 t2) (= a1 a2)))]
diff --git a/hustle/unload.rkt b/hustle/unload.rkt
index 9092ca3..3429e45 100644
--- a/hustle/unload.rkt
+++ b/hustle/unload.rkt
@@ -13,12 +13,12 @@
   (match v
     [(? integer?)    v]
     [(? boolean?)    v]
-    [(? char?)       v]    
+    [(? char?)       v]
     [(? eof-object?) v]
-    [(? void?)       v]    
-    ['()             '()]        
-    [(list 'box a)
+    [(? void?)       v]
+    ['()             '()]
+    [(box-ptr a)
      (box (unload-value (heap-ref h a) h))]
-    [(list 'cons a)
+    [(cons-ptr a)
      (cons (unload-value (heap-ref h a) h)
            (unload-value (heap-ref h (add1 a)) h))]))