Bracket-Matching.md

@@ -59,17 +59,34 @@ ND BixNum[0]     ....................
 Assume that `valueToken` is a bit stream that marks the end position of
 any legal JSON numeral, string or keyword, then the example above would look like:
 ```
-valueToken       ...................1
+valueToken       ...................1.
+EOFbit           ....................1
 ```
 
 Then we can validate if we have valid non-nesting values by checking:
 
 ```
   otherND = bnc.UGT(ND, 0)
+  zeroND = bnc.EQ(ND, 0);
   begin = ~Advance(<1>, 1)
-  firstValue = ScanTo(begin, valueToken)
-  nonNestingValue = ScanTo(Advance(firstValue, 1), valueToken)
-  errSimpleValue = nonNestingValue & ~otherND
+  valueAtZero = valueToken & zeroND
+  stopAtEOF = ~EOFbit
+
+  // If we have simple value at depth 0, we cannot have any other token
+  firstValue = ScanTo(begin, valueAtZero)
+  nonNestedValue = ScanTo(Advance(firstValue, 1), anyToken)
+  errValue = ScanThru(Advance(nonNestedValue, 1), stopAtEOF)
+
+  // If we have any symbol, we cannot have any value at depth 0
+  firstSymbol = ScanTo(begin, symbols)
+  valueAtZeroAfterSymbol = ScanTo(Advance(firstSymbol, 1), valueAtZero)
+  errSymbol = ScanThru(Advance(valueAtZeroAfterSymbol, 1), stopAtEOF)
+
+  // EOFbit is always at depth 0, otherwise we have unmatched parens
+  errEOF = EOFbit & otherND
+
+  // combine all possible errors at depth zero
+  errSimpleValue = errValue | errSymbol | errEOF
 ```