Properly implemented tape-contents function

tm/tmachine.rkt

@@ -103,11 +103,13 @@
             (tape-list->string (cdr (tape-after tape))))))
 
 (define (tape-contents tm)
-  (let ([tape (tm-config-tape tm)])
-    (format "~a~a~a"
-            (tape-list->string (reverse (tape-before tape)))
-            (tape-head tape)
-            (tape-list->string (cdr (tape-after tape))))))
+  (let* ([tape (tm-config-tape tm)]
+         [before (reverse (tape-before tape))]
+         [after (cdr (tape-after tape))])
+    (string-split
+     (apply string-append
+            (map (λ (s) (if (eq? s BLANK) " " (format "~a" s)))
+                 (append before (list (tape-head tape)) after))))))
 
 ;; program-related stuff
 
@@ -181,10 +183,10 @@
              (> (tm-config-steps tm) MAX-STEPS))
       (error (format "TM still running after ~a steps; double-check for possible infinite loop"
                      MAX-STEPS)))
-    (printf "~a\n\t" (stmt->string (vector-ref (tm-config-program tm)
-                            (tm-config-line-no tm))))
+    ;(printf "~a\n\t" (stmt->string (vector-ref (tm-config-program tm)
+    ;                        (tm-config-line-no tm))))
     (step! tm)
-    (print-tape tm)
+    ;(print-tape tm)
     ;(printf "tape position: ~a" (tape-pos (tm-config-tape tm)))
     (if (not (eq? (tm-config-state tm) 'running))
         (tm-config-state tm)
@@ -199,4 +201,3 @@
 
 (define (set-input! tm input)
   (set-tm-config-tape! tm (initial-tape-for input)))
-