The simulator only knows how to match exact bytes. Today you teach its states to match any character and character-class sets, so the NFA covers the same alphabet the backtracker does.
Extend NFA compilation and stepping so Dot and Class nodes match during simulation.
Your simulator’s step loop currently tests s.Ch == ch - it only knows exact bytes.
To match . and [a-z], generalize that test: give each consuming state a way to
answer “do you accept this byte?” A Char accepts one specific byte, an Any state
(compiled from Dot) accepts anything, and a Class state accepts a byte when it is
in the set - or not in it, if negated. The rest of the simulation is unchanged; only
the accept test grows.
Anchors need a quick decision too. Since nfaMatch already matches the whole string,
^ and $ are redundant at the ends - so the simplest correct move for now is to
compile them as pass-through states that consume nothing, exactly like a one-armed
Split. That keeps patterns like ^abc$ working (they mean the same as abc under
whole-string matching). With this, the NFA recognizes the full core syntax - and
tomorrow you get to watch it shrug off the pattern that would hang the backtracker.
// Give a state a way to say "do I accept this byte?":// Char -> byte == Ch// Any -> true (from Dot)// Class -> (byte in Set) != Negate// The step loop calls that test instead of a bare == on Ch.// Anchors: compile ^ and $ to a plain pass-through (Split-like).