diff --git a/beautiful-racket-lib/br/syntax.rkt b/beautiful-racket-lib/br/syntax.rkt
index 3223584..8b3f9a3 100644
--- a/beautiful-racket-lib/br/syntax.rkt
+++ b/beautiful-racket-lib/br/syntax.rkt
@@ -117,4 +117,8 @@
   (check-false (syntax-property* x 'foo))
   (check-true (syntax-property* x 'bar))
   (check-equal? (syntax-property* x 'foo 'bar 'zam) '(#f #t boni)))
+
+(define-syntax-rule (introduce-id (id ...) . body)
+  (with-syntax ([id (syntax-local-introduce (datum->syntax #f 'id))] ...)
+    . body))
   
diff --git a/beautiful-racket/br/demo/hdl-tst/expander.rkt b/beautiful-racket/br/demo/hdl-tst/expander.rkt
index e78fddf..bd9c4af 100644
--- a/beautiful-racket/br/demo/hdl-tst/expander.rkt
+++ b/beautiful-racket/br/demo/hdl-tst/expander.rkt
@@ -1,63 +1,92 @@
 #lang br
-(require (for-syntax br/syntax br/scope racket/string)
-         "hdlprint.rkt" rackunit racket/file)
+(require (for-syntax br/syntax br/scope racket/string) rackunit racket/file)
 (provide #%top-interaction #%module-begin #%datum #%app (all-defined-out))
 
 
+(define (print-cell val fmt)
+  (match-define (list _ radix-letter number-strings) (regexp-match #px"^%(.)(.*)$" fmt)) ; like %B1.16.1
+  (match-define (list left-margin width right-margin) (map string->number (string-split number-strings ".")))
+  (cond
+    [(number? val)
+     (define radix (case radix-letter
+                     [("B") 2]))
+     (string-append (make-string left-margin #\space)
+                    (~r val #:min-width width #:pad-string "0" #:base radix)
+                    (make-string right-margin #\space))]
+    [(string? val) (~a val #:min-width (+ left-margin width right-margin) #:pad-string " " #:align 'center)]
+    [else (error 'unknown-value)]))
+
+
+(define (print-line output-filename cells)
+  (with-output-to-file output-filename
+    (λ () (printf (format "~a\n" (string-join cells "|" #:before-first "|" #:after-last "|"))))
+    #:mode 'text
+    #:exists 'append))
+
+(module+ test
+  (require rackunit)
+  (define a 123)
+  (check-equal? (print-cell a "%B1.16.1") " 0000000001111011 ")
+  (check-equal? (print-cell "out" "%B1.16.1") "       out        ")
+  (check-equal? (print-cell "out" "%B3.1.3") "  out  ")
+  (check-equal? (print-cell "in" "%B3.1.3") "  in   "))
+
+
 (define-for-syntax chip-prefix #f)
 
 
-(define-macro (tst-program ARG ...)
-  (let-shared-id (compare output-file)
-                 #'(begin ARG ...
-                          (close-output-port output-file)
-                          (compare))))
+(define-macro (tst-program EXPR ...)
+  #'(begin
+      EXPR ...
+      (compare-files)))
 
 
 (define-macro (load-expr CHIPFILE-STRING)
   (set! chip-prefix (string-replace (syntax->datum #'CHIPFILE-STRING) ".hdl" ""))
-  (let-syntax-pattern ([CHIPFILE.RKT (format-string "~a.rkt" #'CHIPFILE-STRING)])
-                      #'(require CHIPFILE.RKT)))
+  (let-syntax-pattern
+   ([CHIPFILE.RKT (format-string "~a.rkt" #'CHIPFILE-STRING)])
+   #'(require CHIPFILE.RKT)))
 
 
 (define-macro (output-file-expr OUTPUT-FILE-STRING)
-  (let-shared-id (output-file output-filename)
-                 #'(begin
-                     (define output-filename OUTPUT-FILE-STRING)
-                     (define output-file (open-output-file output-filename #:exists 'replace)))))
+  (introduce-id
+   (output-file output-filename)
+   #'(begin
+       (define output-filename OUTPUT-FILE-STRING)
+       (with-output-to-file output-filename
+         (λ () (printf ""))
+         #:mode 'text
+         #:exists 'replace))))
 
 
 (define-macro (compare-to-expr COMPARE-FILE-STRING)
-  (let-shared-id (compare output-filename)
-                 #'(define (compare)
-                     (check-equal? (file->lines output-filename) (file->lines COMPARE-FILE-STRING)))))
+  (introduce-id
+   (compare-files)
+   #'(define (compare-files)
+       (check-equal? (file->lines output-filename) (file->lines COMPARE-FILE-STRING)))))
 
 
 (define-macro (output-list-expr (COL-NAME FORMAT-SPEC) ...)
-  (let-shared-id (output output-file eval-result eval-thunk)
-                 (let-syntax-pattern ([(COL-ID ...) (suffix-ids #'(COL-NAME ...))]
-                                      [(CHIP-COL-ID ...) (prefix-ids chip-prefix "-" #'(COL-NAME ...))])
-                                     #'(begin
-                                         (define (output COL-ID ...)
-                                           (fprintf output-file
-                                                    (format "~a\n" (string-join (list (hdlprint COL-ID FORMAT-SPEC) ...) "|"
-                                                                                #:before-first "|"
-                                                                                #:after-last "|"))))
-                                         (define eval-result #f)
-                                         (define (eval-thunk) (list (CHIP-COL-ID) ...))
-                                         (output COL-NAME ...)))))
+  (introduce-id
+   (eval-result eval-chip output)
+   (let-syntax-pattern
+    ([(COL-ID ...) (suffix-ids #'(COL-NAME ...))]
+     [(CHIP-COL-ID ...) (prefix-ids chip-prefix "-" #'(COL-NAME ...))])
+    #'(begin
+        (define (output COL-ID ...)
+          (print-line output-filename (map print-cell (list COL-ID ...) (list FORMAT-SPEC ...))))
+        (define eval-result #f)
+        (define (eval-chip) (list (CHIP-COL-ID) ...))
+        (output COL-NAME ...)))))
 
 
 (define-macro (set-expr IN-BUS IN-VAL)
-  (let-syntax-pattern ([CHIP-IN-BUS-ID-WRITE (prefix-id chip-prefix "-" (suffix-id #'IN-BUS "-write"))])
-                      #'(CHIP-IN-BUS-ID-WRITE IN-VAL)))
+  (let-syntax-pattern
+   ([CHIP-IN-BUS-ID-WRITE (prefix-id chip-prefix "-" (suffix-id #'IN-BUS "-write"))])
+   #'(CHIP-IN-BUS-ID-WRITE IN-VAL)))
 
 
-(define-macro (eval-expr)
-  (let-shared-id (eval-result eval-thunk)
-                 #'(set! eval-result (eval-thunk))))
+(define-macro (eval-expr) #'(set! eval-result (eval-chip)))
 
 
-(define-macro (output-expr)
-  (let-shared-id (output eval-result)
-                 #'(apply output eval-result)))
+(define-macro (output-expr) #'(apply output eval-result))
diff --git a/beautiful-racket/br/demo/hdl-tst/hdlprint.rkt b/beautiful-racket/br/demo/hdl-tst/hdlprint.rkt
deleted file mode 100644
index d10ac4e..0000000
--- a/beautiful-racket/br/demo/hdl-tst/hdlprint.rkt
+++ /dev/null
@@ -1,23 +0,0 @@
-#lang racket
-(provide hdlprint)
-
-(define (hdlprint val fmt)
-  (match-define (list _ radix-letter number-strings) (regexp-match #px"^%(.)(.*)$" fmt)) ; like %B1.16.1
-  (match-define (list left-margin width right-margin) (map string->number (string-split number-strings ".")))
-  (cond
-    [(number? val)
-      (define radix (case radix-letter
-                     [("B") 2]))
-        (string-append (make-string left-margin #\space)
-                       (~r val #:min-width width #:pad-string "0" #:base radix)
-                       (make-string right-margin #\space))]
-    [(string? val) (~a val #:min-width (+ left-margin width right-margin) #:pad-string " " #:align 'center)]
-    [else (error 'unknown-value)]))
-
-(module+ test
-  (require rackunit)
-  (define a 123)
-  (check-equal? (hdlprint a "%B1.16.1") " 0000000001111011 ")
-  (check-equal? (hdlprint "out" "%B1.16.1") "       out        ")
-  (check-equal? (hdlprint "out" "%B3.1.3") "  out  ")
-  (check-equal? (hdlprint "in" "%B3.1.3") "  in   "))
diff --git a/beautiful-racket/br/demo/hdl/And.tst.rkt b/beautiful-racket/br/demo/hdl/And.tst.rkt
index 424f178..d4e5d6f 100755
--- a/beautiful-racket/br/demo/hdl/And.tst.rkt
+++ b/beautiful-racket/br/demo/hdl/And.tst.rkt
@@ -1,31 +1,31 @@
-#lang br/demo/hdl-tst
-
-// This file is part of www.nand2tetris.org
-// and the book "The Elements of Computing Systems"
-// by Nisan and Schocken, MIT Press.
-// File name: projects/01/And.tst
-
-load And.hdl,
-output-file And.out,
-compare-to And.cmp,
-output-list a%B3.1.3 b%B3.1.3 out%B3.1.3;
-
-set a 0,
-set b 0,
-eval,
-output;
-
-set a 0,
-set b 1,
-eval,
-output;
-
-set a 1,
-set b 0,
-eval,
-output;
-
-set a 1,
-set b 1,
-eval,
-output;
+#lang br/demo/hdl-tst
+
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/01/And.tst
+
+load And.hdl,
+output-file And.out,
+compare-to And.cmp,
+output-list a%B3.1.3 b%B3.1.3 out%B3.1.3;
+
+set a 0,
+set b 0,
+eval,
+output;
+
+set a 0,
+set b 1,
+eval,
+output;
+
+set a 1,
+set b 0,
+eval,
+output;
+
+set a 1,
+set b 1,
+eval,
+output;
diff --git a/beautiful-racket/br/demo/hdl/expander.rkt b/beautiful-racket/br/demo/hdl/expander.rkt
index e36cf50..ea12692 100644
--- a/beautiful-racket/br/demo/hdl/expander.rkt
+++ b/beautiful-racket/br/demo/hdl/expander.rkt
@@ -6,23 +6,25 @@
                             (in-spec (IN-BUS IN-WIDTH ...) ...)
                             (out-spec (OUT-BUS OUT-WIDTH ...) ...)
                             PART ...)
-  (let-syntax-pattern ([CHIP-PREFIX (suffix-id #'CHIPNAME "-")]
-                       [(IN-BUS-WRITE ...) (suffix-ids #'(IN-BUS ...) "-write")]
-                       [(PREFIX-OUT-BUS ...) (prefix-ids #'CHIP-PREFIX #'(OUT-BUS ...))])
-                      #'(begin
-                          (provide (prefix-out CHIP-PREFIX (combine-out IN-BUS ... IN-BUS-WRITE ...))) 
-                          (define-input-bus IN-BUS IN-WIDTH ...) ...
-                          PART ...
-                          (provide PREFIX-OUT-BUS ...)
-                          (define-output-bus PREFIX-OUT-BUS OUT-BUS OUT-WIDTH ...) ...)))
+  (let-syntax-pattern
+   ([CHIP-PREFIX (suffix-id #'CHIPNAME "-")]
+    [(IN-BUS-WRITE ...) (suffix-ids #'(IN-BUS ...) "-write")]
+    [(PREFIX-OUT-BUS ...) (prefix-ids #'CHIP-PREFIX #'(OUT-BUS ...))])
+   #'(begin
+       (provide (prefix-out CHIP-PREFIX (combine-out IN-BUS ... IN-BUS-WRITE ...))) 
+       (define-input-bus IN-BUS IN-WIDTH ...) ...
+       PART ...
+       (provide PREFIX-OUT-BUS ...)
+       (define-output-bus PREFIX-OUT-BUS OUT-BUS OUT-WIDTH ...) ...)))
 
 
 (define-macro (part PARTNAME ((BUS-LEFT . BUS-LEFT-ARGS) BUS-RIGHT-EXPR) ...)
-  (let-syntax-pattern ([(PARTNAME-BUS-LEFT ...) (prefix-ids #'PARTNAME "-" #'(BUS-LEFT ...))]
-                       [CHIP-MODULE-PATH (format-string "~a.hdl.rkt" #'PARTNAME)])
-                      #'(begin
-                          (require (import-chip CHIP-MODULE-PATH) (for-syntax (import-chip CHIP-MODULE-PATH)))
-                          (handle-buses ((PARTNAME-BUS-LEFT . BUS-LEFT-ARGS) BUS-RIGHT-EXPR) ...))))
+  (let-syntax-pattern
+   ([(PARTNAME-BUS-LEFT ...) (prefix-ids #'PARTNAME "-" #'(BUS-LEFT ...))]
+    [CHIP-MODULE-PATH (format-string "~a.hdl.rkt" #'PARTNAME)])
+   #'(begin
+       (require (import-chip CHIP-MODULE-PATH) (for-syntax (import-chip CHIP-MODULE-PATH)))
+       (handle-buses ((PARTNAME-BUS-LEFT . BUS-LEFT-ARGS) BUS-RIGHT-EXPR) ...))))
 
 
 (define-syntax import-chip
@@ -34,15 +36,17 @@
 
 
 (define-macro (handle-buses BUS-ASSIGNMENTS ...)
-  (let-values ([(in-bus-assignments out-bus-assignments)
-                (syntax-case-partition #'(BUS-ASSIGNMENTS ...) ()
-                                       [((PREFIXED-WIRE . _) _)
-                                        (syntax-local-eval (syntax-shift-phase-level #'(input-bus? PREFIXED-WIRE) 1))])])
-    (let-syntax-pattern ([(((IN-BUS IN-BUS-ARG ...) _in-bus-value) ...) in-bus-assignments]
-                         [(IN-BUS-WRITE ...) (suffix-ids #'(IN-BUS ...) "-write")]
-                         [((OUT-BUS-EXPR (NEW-OUT-BUS)) ...) out-bus-assignments])
-                        #'(begin
-                            (define-output-bus NEW-OUT-BUS
-                              (λ ()
-                                (IN-BUS-WRITE IN-BUS-ARG ... _in-bus-value) ...
-                                OUT-BUS-EXPR)) ...))))
\ No newline at end of file
+  (let-values
+      ([(in-bus-assignments out-bus-assignments)
+        (syntax-case-partition #'(BUS-ASSIGNMENTS ...) ()
+                               [((PREFIXED-WIRE . _) _)
+                                (syntax-local-eval (syntax-shift-phase-level #'(input-bus? PREFIXED-WIRE) 1))])])
+    (let-syntax-pattern
+     ([(((IN-BUS IN-BUS-ARG ...) IN-BUS-VALUE) ...) in-bus-assignments]
+      [(IN-BUS-WRITE ...) (suffix-ids #'(IN-BUS ...) "-write")]
+      [((OUT-BUS-EXPR (NEW-OUT-BUS)) ...) out-bus-assignments])
+     #'(begin
+         (define-output-bus NEW-OUT-BUS
+           (λ ()
+             (IN-BUS-WRITE IN-BUS-ARG ... IN-BUS-VALUE) ...
+             OUT-BUS-EXPR)) ...))))
\ No newline at end of file