data tape inspector works like cli (only shows end state)

gui.rkt

@@ -64,6 +64,8 @@
   (execute-content
    (lambda (ps)
      (define out (prog-state-output ps))
+     ; update data tape inspector
+     (make-tape-cells ps)
      ; set output and change color to ended
      (send RUN-OUTPUT set-value out)
      (send RUN-OUTPUT set-field-background end-col))))
@@ -168,34 +170,32 @@
        [style (list 'auto-hscroll)]
        [stretchable-height #f]))
 
-; make-cell: Number String Boolean -> Canvas
+; make-cell: Nat Byte Boolean -> Canvas
+; Given a cell index, the cell contents, and a boolean set to #t when the cell
+; is pointed by the data pointer, returns the rendered cell as a Canvas.
 (define (make-cell index content hl)
   (new canvas%
        [parent tape-panel]
        [min-height 50]
        [min-width 50]
+       [stretchable-width #f]
        [stretchable-height #f]
        [label (string-append (number->string index) ":")]
        [paint-callback
         (lambda (c dc)
           (send c set-canvas-background (if hl end-col run-col))
-          (send dc draw-text (send c get-label) 12.5 5)
-          (send dc draw-text content 12.5 25))]))
+          (send dc draw-text (send c get-label) 12.5 10)
+          (send dc draw-text content 12.5 30))]))
 
-(make-cell 0 "000" #f)
-(make-cell 1 "255" #t)
-(make-cell 2 "100" #f)
-(make-cell 300000000 "100" #f)
-(make-cell 4 "100" #f)
-(make-cell 5 "100" #f)
-(make-cell 6 "100" #f)
-(make-cell 7 "100" #f)
-(make-cell 8 "100" #f)
-(make-cell 9 "100" #f)
-(make-cell 10 "100" #f)
-(make-cell 11 "100" #f)
-(make-cell 12 "100" #f)
-(make-cell 13 "100" #f)
+; make-tape-cells: ProgState -> _
+; Given a ProgState, empties the data tape inspector and creates the
+; corresponding cells as canvasas in the tape inspector.
+(define (make-tape-cells ps)
+  (define dt (prog-state-tape ps))
+  (send tape-panel change-children (lambda (_) '()))
+  (for ([i (in-range 0 (prog-state-tape-len ps))]
+        [tp dt])
+    (make-cell i (number->string tp) (= i (prog-state-dp ps)))))
 
 ; The input horizontal panel
 (define input-panel

interpreter.rkt

@@ -10,6 +10,7 @@
 (provide prog-state
          prog-state?
          prog-state-tape
+         prog-state-tape-len
          prog-state-dp
          prog-state-output
          prog-state-program