More Kleene star fixes

matching.go

@@ -1,5 +1,22 @@
 package main
 
+// takeZeroState takes the 0-state (if such a transition exists) for all states in the
+// given slice. It returns the resulting states. If any of the resulting states is a 0-state,
+// the second parameter is true.
+func takeZeroState(states []*State) (rtv []*State, isZero bool) {
+	for _, state := range states {
+		if len(state.transitions[EPSILON]) > 0 {
+			rtv = append(rtv, state.transitions[EPSILON]...)
+		}
+	}
+	for _, state := range rtv {
+		if len(state.transitions[EPSILON]) > 0 {
+			return rtv, true
+		}
+	}
+	return rtv, false
+}
+
 // match tries to match the regex represented by given start-state, with
 // the given string
 func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
@@ -18,14 +35,16 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 
 	// Main loop
 	for i < len(str) {
-		// If there are any 0-transitions, take those
-		// TODO: Maybe I need to keep taking 0-transitions until I don't have anymore. Needs to be tested
-		for _, state := range currentStates {
-			if len(state.transitions[EPSILON]) > 0 {
-				tempStates = append(tempStates, state.transitions[EPSILON]...)
-			}
+		zeroStates := make([]*State, 0)
+		// Keep taking zero-states, until there are no more left to take
+		zeroStates, isZero := takeZeroState(currentStates)
+		tempStates = append(tempStates, zeroStates...)
+		for isZero == true {
+			zeroStates, isZero = takeZeroState(tempStates)
+			tempStates = append(tempStates, zeroStates...)
 		}
-		copy(currentStates, tempStates)
+
+		currentStates = append(currentStates, tempStates...)
 		tempStates = nil
 
 		// Take any transitions corresponding to current character
@@ -40,6 +59,7 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 				}
 			}
 		}
+		currentStates = make([]*State, len(tempStates))
 		copy(currentStates, tempStates)
 		tempStates = nil
 
@@ -52,7 +72,7 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 			tempStates = append(tempStates, state.transitions[EPSILON]...)
 		}
 	}
-	copy(currentStates, tempStates)
+	currentStates = append(currentStates, tempStates...)
 	tempStates = nil
 
 	for _, state := range currentStates {