diff --git a/codegen/codegen.rkt b/codegen/codegen.rkt
old mode 100755
new mode 100644
index 9dac33c..a007d64
--- a/codegen/codegen.rkt
+++ b/codegen/codegen.rkt
@@ -35,7 +35,7 @@
   (define translated-patterns
     (let loop ([primitive-patterns (syntax->list a-clause)])
       (cond
-        [(empty? primitive-patterns) null]
+        [(empty? primitive-patterns) '()]
         [else
          (cons (syntax-case (first primitive-patterns) (id lit token inferred-id)
                  [(id val)
@@ -104,7 +104,7 @@
 ;; of explicit token types, though the user is not allow to express it themselves.
 (define (rules-collect-token-types rules)
   (define-values (implicit explicit)
-    (for/fold ([implicit null]
+    (for/fold ([implicit '()]
                [explicit (list (datum->syntax (first rules) 'EOF))])
               ([a-rule (in-list rules)])
       (syntax-case a-rule (rule)
@@ -187,7 +187,7 @@
 (define (rule-collect-used-ids a-rule)
   (syntax-case a-rule (rule)
     [(rule id a-pattern)
-     (pattern-collect-used-ids #'a-pattern null)]))
+     (pattern-collect-used-ids #'a-pattern '())]))
 
 ;; pattern-collect-used-ids: pattern-stx (listof identifier) -> (listof identifier)
 ;; Returns a flat list of rule identifiers referenced in the pattern.
@@ -228,7 +228,7 @@
     (make-free-id-table (for/list ([a-rule (in-list rules)])
                           (cons (rule-id a-rule) (sat:make-and)))))
   
-  (define leaves null)
+  (define leaves '())
   
   (define (make-leaf)
     (define a-leaf (sat:make-and))
diff --git a/parser-tools/cfg-parser.rkt b/parser-tools/cfg-parser.rkt
index b7094b9..d76f960 100644
--- a/parser-tools/cfg-parser.rkt
+++ b/parser-tools/cfg-parser.rkt
@@ -138,7 +138,7 @@
     (report-answer answer-key
                    max-depth
                    tasks
-                   null))
+                   '()))
   (let* ([tasks (queue-task tasks (λ (max-depth tasks)
                                     (parse-a gota-k faila-k max-depth tasks)))]
          [tasks (queue-task tasks (λ (max-depth tasks)
@@ -217,7 +217,7 @@
 
 ;; Reports an answer to multiple waiting threads:
 (define (report-answer-all answer-key max-depth ts val k)
-  (define v (hash-ref (tasks-multi-waits ts) answer-key (λ () null)))
+  (define v (hash-ref (tasks-multi-waits ts) answer-key (λ () '())))
   (hash-remove! (tasks-multi-waits ts) answer-key)
   (let ([ts (tasks (append (map (λ (a) (a val)) v)
                                    (tasks-active ts))
@@ -243,7 +243,7 @@
     (if multi?
         (hash-set! (tasks-multi-waits ts) answer-key
                    (cons wait (hash-ref (tasks-multi-waits ts) answer-key
-                                        (λ () null))))
+                                        (λ () '()))))
         (hash-set! (tasks-waits ts) answer-key wait))
     (let ([ts (tasks (tasks-active ts)
                              (tasks-active-back ts)
@@ -260,7 +260,7 @@
       (if (tasks-progress? ts)
           (swap-task max-depth
                      (tasks (reverse (tasks-active-back ts))
-                                 null
+                                 '()
                                  (tasks-waits ts)
                                  (tasks-multi-waits ts)
                                  (tasks-cache ts)
@@ -332,7 +332,7 @@
                                  [#,id-end-pos (at-tok-pos #'tok-end #'last-consumed-token)]
                                  #,@(if n-end-pos
                                         #`([#,n-end-pos (at-tok-pos #'tok-end #'last-consumed-token)])
-                                        null))
+                                        '()))
                       #,(loop (cdr pat) (add1 pos)))))
                 stream last-consumed-token depth 
                 #,(let ([cnt (for/sum ([item (in-list (cdr pat))])
@@ -357,7 +357,7 @@
                                       [#,id-end-pos (at-tok-pos #'tok-end #'stream-a)]
                                       #,@(if n-end-pos
                                              #`([#,n-end-pos (at-tok-pos #'tok-end #'stream-a)])
-                                             null))
+                                             '()))
                            #,(loop (cdr pat) (add1 pos)))))
                      (fail-k max-depth tasks)))])))))
 
@@ -444,7 +444,7 @@
                (report-answer-all answer-key
                                   max-depth
                                   tasks
-                                  null
+                                  '()
                                   (λ (max-depth tasks)
                                     (fail-k max-depth tasks))))
              (k end max-depth tasks new-got-k new-fail-k))]))))
@@ -476,21 +476,21 @@
                                                                 [(e-terminals-def? v)
                                                                  (for/list ([v (in-list (syntax->list (e-terminals-def-t v)))])
                                                                            (cons v #t))]
-                                                                [else null])))]
-                                                  [_else null])))]
+                                                                [else '()])))]
+                                                  [_else '()])))]
                            [all-end-toks (apply
                                           append
                                           (for/list ([clause (in-list clauses)])
                                                     (syntax-case clause (end)
                                                       [(end T ...)
                                                        (syntax->list #'(T ...))]
-                                                      [_else null])))])
+                                                      [_else '()])))])
                        (let loop ([clauses clauses]
                                   [cfg-start #f]
                                   [cfg-grammar #f]
                                   [cfg-error #f]
                                   [src-pos? #f]
-                                  [parser-clauses null])
+                                  [parser-clauses '()])
                          (if (null? clauses)
                              (values cfg-start
                                      cfg-grammar
@@ -554,7 +554,7 @@
                                                   (if (zero? (car l))
                                                       (append (cdr l) (loop (cdr pat)))
                                                       (cdr l)))
-                                                null)))))
+                                                '())))))
                                      (define new
                                        (filter (λ (id)
                                                  (andmap (λ (id2)
diff --git a/parser-tools/examples/read.rkt b/parser-tools/examples/read.rkt
index c461a22..80290c2 100644
--- a/parser-tools/examples/read.rkt
+++ b/parser-tools/examples/read.rkt
@@ -47,7 +47,7 @@
                        (get-string-token input-port))]
    [(:: #\\ #\\) (cons #\\ (get-string-token input-port))]
    [(:: #\\ #\") (cons #\" (get-string-token input-port))]
-   [#\" null]))
+   [#\" '()]))
   
   
 (define-lex-abbrevs
@@ -226,7 +226,7 @@
           [(UNQUOTE-SPLICING sexp) (build-so (list 'unquote-splicing $2) 1 2)]
           [(OP sexp-list DOT sexp CP) (build-so (append (reverse $2) $4) 1 5)])
       
-    (sexp-list [() null]
+    (sexp-list [() '()]
                [(sexp-list sexp) (cons $2 $1)]))))
   
 (define (rs sn ip)
diff --git a/parser-tools/private-lex/deriv.rkt b/parser-tools/private-lex/deriv.rkt
index 404fb9b..7750e98 100644
--- a/parser-tools/private-lex/deriv.rkt
+++ b/parser-tools/private-lex/deriv.rkt
@@ -17,7 +17,7 @@
 ;; taking the derivative of r.
 (define (get-char-groups r found-negation)
   (cond
-    [(or (eq? r e) (eq? r z)) null]
+    [(or (eq? r e) (eq? r z)) '()]
     [(char-setR? r) (list r)]
     [(concatR? r)
      (if (re-nullable? (concatR-re1 r))
@@ -38,8 +38,8 @@
 (test-block ((c (make-cache))
              (r1 (->re #\1 c))
              (r2 (->re #\2 c)))
-            ((get-char-groups e #f) null)
-            ((get-char-groups z #f) null)
+            ((get-char-groups e #f) '())
+            ((get-char-groups z #f) '())
             ((get-char-groups r1 #f) (list r1))
             ((get-char-groups (->re `(concatenation ,r1 ,r2) c) #f)
              (list r1))
@@ -142,7 +142,7 @@
 (test-block ((c (make-cache))
              (r1 (->re #\1 c))
              (r2 (->re #\2 c)))
-            ((derive null (char->integer #\1) c) #f)
+            ((derive '() (char->integer #\1) c) #f)
             ((derive (list (cons r1 1) (cons r2 2)) (char->integer #\1) c)
              (list (cons e 1) (cons z 2)))
             ((derive (list (cons r1 1) (cons r2 2)) (char->integer #\3) c) #f))
@@ -163,7 +163,7 @@
              (r2 (->re #\b c))
              (b (list (cons z 1) (cons z 2) (cons z 3) (cons e 4) (cons z 5)))
              (a (list (cons r1 1) (cons r2 2))))
-            ((derive null (c->i #\a) c) #f)
+            ((derive '() (c->i #\a) c) #f)
             ((derive a (c->i #\a) c) (list (cons e 1) (cons z 2)))
             ((derive a (c->i #\b) c) (list (cons z 1) (cons e 2)))
             ((derive a (c->i #\c) c) #f)
@@ -194,7 +194,7 @@
 ;; derivative of the car of st.  Only one derivative per set need to be taken.
 (define (compute-chars st)
   (cond
-    [(null? st) null]
+    [(null? st) '()]
     [else
      (loc:partition (map char-setR-chars
                          (apply append (map (λ (x) (get-char-groups (car x) #f))
@@ -204,8 +204,8 @@
              (c->i char->integer)
              (r1 (->re `(char-range #\1 #\4) c))
              (r2 (->re `(char-range #\2 #\3) c)))
-            ((compute-chars null) null)
-            ((compute-chars (list (state null 1))) null)
+            ((compute-chars '()) '())
+            ((compute-chars (list (state '() 1))) '())
             ((map is:integer-set-contents
                   (compute-chars (list (state (list (cons r1 1) (cons r2 2)) 2))))
              (list (is:integer-set-contents (is:make-range (c->i #\2) (c->i #\3)))
@@ -229,7 +229,7 @@
          [start (state rs (get-state-number))])
     (cache (cons 'state (get-key rs)) (λ () start))
     (let loop ([old-states (list start)]
-               [new-states null]
+               [new-states '()]
                [all-states (list start)]
                [cs (compute-chars (list start))])
       (cond
@@ -248,7 +248,7 @@
                                                            (state-index (cdr t)))))))
                          < #:key car))]
         [(null? old-states)
-         (loop new-states null all-states (compute-chars new-states))]
+         (loop new-states '() all-states (compute-chars new-states))]
         [(null? cs)
          (loop (cdr old-states) new-states all-states (compute-chars (cdr old-states)))]
         [else
@@ -267,7 +267,7 @@
                          s
                          (cons (cons c new-state)
                                (hash-ref transitions s
-                                         (λ () null))))
+                                         (λ () '()))))
               (cond
                 [new-state?
                  (loop old-states (cons new-state new-states) new-all-states (cdr cs))]
diff --git a/parser-tools/private-lex/re.rkt b/parser-tools/private-lex/re.rkt
index 8e1cfc0..9954af7 100644
--- a/parser-tools/private-lex/re.rkt
+++ b/parser-tools/private-lex/re.rkt
@@ -117,7 +117,7 @@
   (let loop ([res l]
              ;; chars : (union #f char-set)
              [chars #f]
-             [no-chars null])
+             [no-chars '()])
     (cond
       [(null? res) 
        (if chars
@@ -189,7 +189,7 @@
   (let ([rs 
          (filter
           (λ (x) (not (eq? x z)))
-          (do-simple-equiv (replace rs orR? orR-res null) re-index))])
+          (do-simple-equiv (replace rs orR? orR-res '()) re-index))])
     (cond
       [(null? rs) z]
       [(null? (cdr rs)) (car rs)]
@@ -201,7 +201,7 @@
   
 ;; build-and : (list-of re) cache -> re
 (define (build-and rs cache)
-  (let ([rs (do-simple-equiv (replace rs andR? andR-res null) re-index)])
+  (let ([rs (do-simple-equiv (replace rs andR? andR-res '()) re-index)])
     (cond
       [(null? rs) (build-neg z cache)]
       [(null? (cdr rs)) (car rs)]
@@ -260,7 +260,7 @@
             (ro4 (build-or `(,r1 ,r2 ,r3) c))
             ((orR-res ro) (list rc rr))
             ((orR-res ro4) (list r1 r2 r3))
-            ((build-or null c) z)
+            ((build-or '() c) z)
             ((build-or `(,r1 ,z) c) r1)
             ((build-repeat 0 +inf.0 rc c) rr)
             ((build-repeat 0 1 z c) e)
@@ -280,7 +280,7 @@
             (ra4 (build-and `(,r1 ,r2 ,r3) c))
             ((andR-res ra) (list rc rr))
             ((andR-res ra4) (list r1 r2 r3))
-            ((build-and null c) (build-neg z c))
+            ((build-and '() c) (build-neg z c))
             ((build-and `(,r1 ,z) c) z)
             ((build-and `(,r1) c) r1)
             ((build-neg r1 c) (build-neg r1 c))
@@ -308,7 +308,7 @@
              (r4 (build-or `(,r1 ,r2) c))
              (r5 (->re `(union ,r3-5 #\7) c))
              (r6 (->re #\6 c)))
-            ((flatten-res null orR? orR-res is:union c) null)
+            ((flatten-res '() orR? orR-res is:union c) '())
             ((isc (char-setR-chars (car (flatten-res `(,r1) orR? orR-res is:union c))))
              (isc (is:make-range (char->integer #\1))))
             ((isc (char-setR-chars (car (flatten-res `(,r4) orR? orR-res is:union c))))
diff --git a/parser-tools/private-lex/unicode-chars.rkt b/parser-tools/private-lex/unicode-chars.rkt
index a6dd678..d5e15f1 100644
--- a/parser-tools/private-lex/unicode-chars.rkt
+++ b/parser-tools/private-lex/unicode-chars.rkt
@@ -9,7 +9,7 @@
 ;; get-chars-for-x : (nat -> bool) (listof (list nat nat bool)) -> (listof (cons nat nat))
 (define (get-chars-for char-x? mapped-chars)
   (cond
-    [(null? mapped-chars) null]
+    [(null? mapped-chars) '()]
     [else
      (define range (car mapped-chars))
      (define low (car range))
diff --git a/parser-tools/private-lex/util.rkt b/parser-tools/private-lex/util.rkt
index 8a279e6..30f685e 100644
--- a/parser-tools/private-lex/util.rkt
+++ b/parser-tools/private-lex/util.rkt
@@ -83,23 +83,23 @@
 
 (module+ test
   (check-equal? (remove-dups '((1 2) (2 2) (1 3) (1 4)
-                                     (100 4) (0 5)) cadr null)
+                                     (100 4) (0 5)) cadr '())
                 '((1 2) (1 3) (1 4) (0 5)))
-  (check-equal? (remove-dups null error null) null))
+  (check-equal? (remove-dups '() error '()) '()))
 
 ;; do-simple-equiv : (list-of X) (X -> nat) -> (list-of X)
 ;; Sorts l according to index and removes the entries with duplicate
 ;; indexes.
 (define (do-simple-equiv l index)
   (define ordered (sort l < #:key index))
-  (remove-dups ordered index null))
+  (remove-dups ordered index '()))
 
 (module+ test
   (check-equal? (do-simple-equiv '((2 2) (1 4) (1 2)
                                          (100 4) (1 3)  (0 5)) 
                                  cadr)
                 '((2 2) (1 3) (1 4) (0 5)))
-  (check-equal? (do-simple-equiv null error) null))
+  (check-equal? (do-simple-equiv '() error) '()))
 
 ;; replace : (list-of X) (X -> bool) (X -> (list-of X)) (list-of X) ->
 ;;           (list-of X)
@@ -113,11 +113,11 @@
 
 
 (module+ test
-  (check-equal? (replace null void (λ () (list 1)) null) null)
+  (check-equal? (replace '() void (λ () (list 1)) '()) '())
   (check-equal? (replace '(1 2 3 4 3 5)
                          (λ (x) (= x 3))
                          (λ (x) (list 1 2 3))
-                         null)
+                         '())
                 '(5 1 2 3 4 1 2 3 2 1)))
   
   
diff --git a/parser-tools/private-yacc/grammar.rkt b/parser-tools/private-yacc/grammar.rkt
index b97abd9..46126e9 100644
--- a/parser-tools/private-yacc/grammar.rkt
+++ b/parser-tools/private-yacc/grammar.rkt
@@ -234,7 +234,7 @@
   ;; of productions that we don't know about yet. 
   (define (set-nullables prods)
     (cond
-      [(null? prods) null]
+      [(null? prods) '()]
       [(vector-ref nullable (gram-sym-index (prod-lhs (car prods))))
        (set-nullables (cdr prods))]
       [(vector-andmap (λ (nt) (vector-ref nullable (gram-sym-index nt))) (prod-rhs (car prods)))
diff --git a/parser-tools/private-yacc/graph.rkt b/parser-tools/private-yacc/graph.rkt
index 620ebb9..0d6bb4c 100644
--- a/parser-tools/private-yacc/graph.rkt
+++ b/parser-tools/private-yacc/graph.rkt
@@ -18,7 +18,7 @@
   (define N (make-hasheq))
   (define (get-N x) (hash-ref N x zero-thunk))
   (define (set-N x d) (hash-set! N x d))
-  (define stack null)
+  (define stack '())
   (define (push x) (set! stack (cons x stack)))
   (define (pop) (begin0 
                   (car stack)
diff --git a/parser-tools/private-yacc/input-file-parser.rkt b/parser-tools/private-yacc/input-file-parser.rkt
index 0c1c35d..cdbfbbd 100644
--- a/parser-tools/private-yacc/input-file-parser.rkt
+++ b/parser-tools/private-yacc/input-file-parser.rkt
@@ -28,7 +28,7 @@
   (define args
     (let get-args ([i i][rhs rhs])
       (cond
-        [(null? rhs) null]
+        [(null? rhs) '()]
         [else
          (define b (car rhs))
          (define name (if (hash-ref empty-table (syntax->datum (car rhs)) #f)
@@ -149,7 +149,7 @@
                     "Associativity must be left, right or nonassoc"
                     type))
                  (syntax->datum prec-decls)]))]
-      [#f null]
+      [#f '()]
       [_ (raise-syntax-error
           'parser-precedences
           "Precedence declaration must be of the form (precs (assoc term ...) ...) where assoc is left, right or nonassoc"
diff --git a/parser-tools/private-yacc/lalr.rkt b/parser-tools/private-yacc/lalr.rkt
index f2cf51b..3c11078 100644
--- a/parser-tools/private-yacc/lalr.rkt
+++ b/parser-tools/private-yacc/lalr.rkt
@@ -53,7 +53,7 @@
   (define rhs-l (vector-length rhs))
   (append (if (and (> rhs-l 0) (eq? nt (vector-ref rhs (sub1 rhs-l))))
               (list (item prod (sub1 rhs-l)))
-              null)
+              '())
           (let loop ([i (sub1 rhs-l)])
             (cond
               [(and (> i 0) 
@@ -63,7 +63,7 @@
                    (cons (item prod (sub1 i))
                          (loop (sub1 i)))
                    (loop (sub1 i)))]
-              [else null]))))
+              [else '()]))))
 
 ;; prod-list->items-for-include: grammar * prod list * non-term -> lr0-item list
 ;; return the list of all (B -> beta . nt gamma) such that  (B -> beta nt gamma) in prod-list
@@ -74,7 +74,7 @@
 ;; comput-includes: lr0-automaton * grammar -> (trans-key -> trans-key list)
 (define (compute-includes a g)
   (define num-states (send a get-num-states))
-  (define items-for-input-nt (make-vector (grammar-num-non-terms g) null))
+  (define items-for-input-nt (make-vector (grammar-num-non-terms g) '()))
   (for ([input-nt (in-list (grammar-non-terms g))])
        (vector-set! items-for-input-nt (non-term-index input-nt)
                     (prod-list->items-for-include g (grammar-all-prods g) input-nt)))
@@ -213,7 +213,7 @@
   (define get-f (lookup-tk-map results))
   (define set-f (add-tk-map results))
              
-  (define stack null)
+  (define stack '())
   (define (push x) (set! stack (cons x stack)))
   (define (pop) (begin0 
                   (car stack)
diff --git a/parser-tools/private-yacc/lr0.rkt b/parser-tools/private-yacc/lr0.rkt
index 63a4f5a..9684822 100644
--- a/parser-tools/private-yacc/lr0.rkt
+++ b/parser-tools/private-yacc/lr0.rkt
@@ -28,7 +28,7 @@
 (define (trans-key-list-remove-dups tkl)
   (let loop ([sorted (sort tkl trans-key<?)])
     (cond
-      [(null? sorted) null]
+      [(null? sorted) '()]
       [(null? (cdr sorted)) sorted]
       [(and (= (non-term-index (trans-key-gs (car sorted)))
                (non-term-index (trans-key-gs (cadr sorted))))
@@ -59,7 +59,7 @@
 (define (reverse-assoc assoc)
   (define reverse-hash (make-hash))
   (define (hash-table-add! ht k v)
-    (hash-set! ht k (cons v (hash-ref ht k (λ () null)))))
+    (hash-set! ht k (cons v (hash-ref ht k (λ () '())))))
   (for ([trans-key/kernel (in-list assoc)])
        (define tk (car trans-key/kernel))
        (hash-table-add! reverse-hash 
@@ -126,7 +126,7 @@
       (for*/list ([k (in-list k)]
                   [val (in-list (hash-ref (vector-ref reverse-transitions (kernel-index k))
                                           (gram-sym-symbol s)
-                                          (λ () null)))])
+                                          (λ () '())))])
                  val))))
 
 (define ((union comp<?) l1 l2)
@@ -171,14 +171,14 @@
                             (grammar-prods-for-non-term grammar nt))))
              (λ (nt) (list nt))
              (union non-term<?)
-             (λ () null)))
+             (λ () '())))
              
   ;; closure: LR1-item list -> LR1-item list
   ;; Creates a set of items containing i s.t. if A -> n.Xm is in it,
   ;; X -> .o is in it too.
   (define (LR0-closure i)
     (cond
-      [(null? i) null]
+      [(null? i) '()]
       [else
        (define next-gsym (sym-at-dot (car i)))
        (cond
@@ -192,8 +192,8 @@
          [else (cons (car i) (LR0-closure (cdr i)))])]))
   
   ;; maps trans-keys to kernels
-  (define automaton-term null)
-  (define automaton-non-term null)
+  (define automaton-term '())
+  (define automaton-non-term '())
              
   ;; keeps the kernels we have seen, so we can have a unique
   ;; list for each kernel
@@ -216,11 +216,11 @@
     (define (add-item! table i)
       (define gs (sym-at-dot i))
       (cond
-        [gs (define already (hash-ref table (gram-sym-symbol gs) (λ () null)))
+        [gs (define already (hash-ref table (gram-sym-symbol gs) (λ () '())))
             (unless (member i already)
               (hash-set! table (gram-sym-symbol gs) (cons i already)))]
         ((zero? (vector-length (prod-rhs (item-prod i))))
-         (define current (hash-ref epsilons ker (λ () null)))
+         (define current (hash-ref epsilons ker (λ () '())))
          (hash-set! epsilons ker (cons i current)))))
     
     ;; Group the items of the LR0 closure of the kernel
@@ -235,9 +235,9 @@
     (define is
       (let loop ([gsyms grammar-symbols])
         (cond
-          [(null? gsyms) null]
+          [(null? gsyms) '()]
           [else
-           (define items (hash-ref table (gram-sym-symbol (car gsyms)) (λ () null)))
+           (define items (hash-ref table (gram-sym-symbol (car gsyms)) (λ () '())))
            (cond
              [(null? items) (loop (cdr gsyms))]
              [else (cons (list (car gsyms) items)
@@ -278,7 +278,7 @@
                            k))
   (define new-kernels (make-queue))
   (let loop ([old-kernels startk]
-             [seen-kernels null])
+             [seen-kernels '()])
     (cond
       [(and (empty-queue? new-kernels) (null? old-kernels))
        (make-object lr0%  automaton-term automaton-non-term
@@ -290,16 +290,16 @@
 
 (struct q (f l) #:mutable)
 (define (empty-queue? q) (null? (q-f q)))
-(define (make-queue) (q null null))
+(define (make-queue) (q '() '()))
 
 (define (enq! q i)
   (cond
     [(empty-queue? q)
-     (let ([i (mcons i null)])
+     (let ([i (mcons i '())])
        (set-q-l! q i)
        (set-q-f! q i))]
     [else
-     (set-mcdr! (q-l q) (mcons i null))
+     (set-mcdr! (q-l q) (mcons i '()))
      (set-q-l! q (mcdr (q-l q)))]))
 
 
diff --git a/parser-tools/private-yacc/parser-builder.rkt b/parser-tools/private-yacc/parser-builder.rkt
index 37b85b0..10ed49a 100644
--- a/parser-tools/private-yacc/parser-builder.rkt
+++ b/parser-tools/private-yacc/parser-builder.rkt
@@ -57,7 +57,7 @@
                           (syntax-case assocs ()
                             (((__ TERM ...) ...)
                              (syntax->list #'(TERM ... ...)))))
-                     null)])
+                     '())])
     #`(when #f
         (let ((BIND void) ... (TMP void) ...)
           (void BOUND ... ... TERM-GROUP ... START ... END ... PREC ...)))))
diff --git a/parser-tools/private-yacc/table.rkt b/parser-tools/private-yacc/table.rkt
index 691ef2e..faa1a82 100644
--- a/parser-tools/private-yacc/table.rkt
+++ b/parser-tools/private-yacc/table.rkt
@@ -18,7 +18,7 @@
   
 ;; make-parse-table : int -> parse-table
 (define (make-parse-table num-states)
-  (make-vector num-states null))
+  (make-vector num-states '()))
   
 ;; table-add!: parse-table nat symbol action ->
 (define (table-add! table state-index symbol val)
@@ -30,7 +30,7 @@
   (for/vector ([state-entry (in-list (vector->list table))])
     (define ht (make-hasheq))
     (for* ([gs/actions (in-list state-entry)]
-           [group (in-value (hash-ref ht (car gs/actions) (λ () null)))]
+           [group (in-value (hash-ref ht (car gs/actions) (λ () '())))]
            #:unless (member (cdr gs/actions) group))
       (hash-set! ht (car gs/actions) (cons (cdr gs/actions) group)))
     (hash-map ht cons)))
@@ -185,7 +185,7 @@
         (list reduce)]
        [(eq? 'right (prec-assoc shift-prec))
         (list shift)]
-       [else null])]
+       [else '()])]
     [else actions]))
     
   
@@ -226,7 +226,7 @@
                        (kernel-index to-state))))))
   (send a for-each-state
         (λ (state)
-          (for ([item (in-list (append (hash-ref (send a get-epsilon-trans) state (λ () null))
+          (for ([item (in-list (append (hash-ref (send a get-epsilon-trans) state (λ () '()))
                                        (filter (λ (item)
                                                  (not (move-dot-right item)))
                                                (kernel-items state))))])
diff --git a/parser-tools/yacc.rkt b/parser-tools/yacc.rkt
index 47e78e7..5bb8a27 100644
--- a/parser-tools/yacc.rkt
+++ b/parser-tools/yacc.rkt
@@ -272,7 +272,7 @@
                  (let-values ([(new-stack args)
                                (reduce-stack stack 
                                              (runtime-reduce-rhs-length action)
-                                             null
+                                             '()
                                              src-pos)])
                    (define goto 
                      (runtime-goto-state
diff --git a/support.rkt b/support.rkt
old mode 100755
new mode 100644
index 49178cd..fd6ff22
--- a/support.rkt
+++ b/support.rkt
@@ -95,7 +95,7 @@
   (define p (if (string? port-or-string)
                 (open-input-string port-or-string)
                 port-or-string))
-  (let loop ([acc null])
+  (let loop ([acc '()])
     (define-values (lex cat shape start end) (colorer p))
     (if (or (eq? 'eof cat) (eof-object? lex))
         (reverse acc)