BAS: Remove some code that I removed too aggressively

interpreters/bas/fs.c

@@ -78,6 +78,8 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <nuttx/ascii.h>
+
 #include "fs.h"
 
 /****************************************************************************
@@ -279,32 +281,68 @@ static int edit(int chn, int onl)
           return -1;
         }
 
+      /* Check for the backspace charactor */
+
+      if (ch == ASCII_BS)
+        {
+          if (f->inCapacity)
+            {
 #ifdef CONFIG_INTERPREPTER_BAS_VT100
-      /* REVISIT: Use VT100 commands to erase */
+              /* REVISIT: Use VT100 commands to erase: Move cursor back and erase to the end of the line */
 #warning Missing Logic
 #else
-      if ((f->inCapacity + 1) < sizeof(f->inBuf))
+              /* Use backspace to erase */
+
+              if (f->inBuf[f->inCapacity - 1] >= '\0' &&
+                  f->inBuf[f->inCapacity - 1] < ' ')
+                {
+                  FS_putChars(chn, "\b\b  \b\b");
+                }
+              else
+                {
+                  FS_putChars(chn, "\b \b");
+                }
+#endif
+              --f->inCapacity;
+            }
+        }
+
+      /* Is there space for another character in the buffer? */
+
+      else if ((f->inCapacity + 1) < sizeof(f->inBuf))
         {
+          /* Yes.. Was this a new line character? */
+
           if (ch != '\n')
             {
+              /* No.. was this an ASCII control character? */
+
               if (ch >= '\0' && ch < ' ')
                 {
+                  /* Yes.. Echo control characters as escape sequences */
+
                   FS_putChar(chn, '^');
                   FS_putChar(chn, ch ? (ch + 'a' - 1) : '@');
                 }
               else
                 {
+                  /* No.. Just echo the character */
+
                   FS_putChar(chn, ch);
                 }
             }
+
+          /* Should we echo newline characters? */
+
           else if (onl)
             {
               FS_putChar(chn, '\n');
             }
 
+          /* Put the raw character into the buffer in any event */
+
           f->inBuf[f->inCapacity++] = ch;
         }
-#endif
     }
   while (ch != '\n');