Removed unnecessary duplication of assertion checking

nfa.go

@@ -111,17 +111,10 @@ func (s State) matchesFor(str []rune, idx int) ([]*State, int) {
 	// Assertions can be viewed as 'checks'. If the check fails, we return
 	// an empty array and 0.
 	// If it passes, we treat it like any other state, and return all the transitions.
-	if s.assert == SOS && idx != 0 {
-		return make([]*State, 0), -1
-	}
-	if s.assert == EOS && idx != len(str) {
-		return make([]*State, 0), -1
-	}
-	if s.assert == WBOUND && !isWordBoundary(str, idx) {
+	if s.assert != NONE {
+		if s.checkAssertion(str, idx) == false {
 			return make([]*State, 0), -1
 		}
-	if s.assert == NONWBOUND && isWordBoundary(str, idx) {
-		return make([]*State, 0), -1
 	}
 	listTransitions := s.transitions[int(str[idx])]
 	for _, dest := range s.transitions[int(ANY_CHAR)] {