Used 'unique append' to ensure that a transition can only contain a given state once

main.go

@@ -147,8 +147,13 @@ func thompson(re string) *State {
 			s3.transitions = make(map[int][]*State)
 			s3.output = append(s3.output, s1.output...)
 			s3.output = append(s3.output, s2.output...)
-			s3.transitions[s1.content] = append(s3.transitions[s1.content], s1)
-			s3.transitions[s2.content] = append(s3.transitions[s2.content], s2)
+			// Unique append is used here (and elsewhere) to ensure that,
+			// for any given transition, a state can only be mentioned once.
+			// For example, given the transition 'a', the state 's1' can only be mentioned once.
+			// This would lead to multiple instances of the same set of match indices, since both
+			// 's1' states would be considered to match.
+			s3.transitions[s1.content] = unique_append(s3.transitions[s1.content], s1)
+			s3.transitions[s2.content] = unique_append(s3.transitions[s2.content], s2)
 			s3.content = EPSILON
 			s3.isEmpty = true
 

nfa.go

@@ -55,7 +55,7 @@ func verifyLastStates(start []*State) {
 
 func concatenate(s1 *State, s2 *State) *State {
 	for i := range s1.output {
-		s1.output[i].transitions[s2.content] = append(s1.output[i].transitions[s2.content], s2)
+		s1.output[i].transitions[s2.content] = unique_append(s1.output[i].transitions[s2.content], s2)
 	}
 	s1.output = s2.output
 	return s1
@@ -69,8 +69,8 @@ func kleene(s1 State) *State {
 	toReturn.isKleene = true
 	toReturn.output = append(toReturn.output, toReturn)
 	for i := range s1.output {
-		s1.output[i].transitions[toReturn.content] = append(s1.output[i].transitions[toReturn.content], toReturn)
+		s1.output[i].transitions[toReturn.content] = unique_append(s1.output[i].transitions[toReturn.content], toReturn)
 	}
-	toReturn.transitions[s1.content] = append(toReturn.transitions[s1.content], &s1)
+	toReturn.transitions[s1.content] = unique_append(toReturn.transitions[s1.content], &s1)
 	return toReturn
 }