Initial support for multiple matching

main.go

@@ -178,14 +178,21 @@ func main() {
 	re_postfix := shuntingYard(re)
 	// fmt.Println(re_postfix)
 	startState := thompson(re_postfix)
-	start, end, matched := match(startState, os.Args[2])
-	if matched {
+	matchIndices := match(startState, os.Args[2])
+	inColor := false
+	if len(matchIndices) > 0 {
 		for i, c := range os.Args[2] {
-			if i >= start && i < end {
-				color.New(color.FgRed).Printf("%c", c)
-			} else {
+			for _, indices := range matchIndices {
+				if i >= indices.startIdx && i < indices.endIdx {
+					color.New(color.FgRed).Printf("%c", c)
+					inColor = true
+					break
+				}
+			}
+			if inColor == false {
 				fmt.Printf("%c", c)
 			}
+			inColor = false
 		}
 		fmt.Printf("\n")
 	} else {

matching.go

@@ -1,5 +1,11 @@
 package main
 
+// a matchIndex represents a match. It contains the start index and end index of the match
+type matchIndex struct {
+	startIdx int
+	endIdx   int
+}
+
 // 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.
@@ -19,7 +25,17 @@ func takeZeroState(states []*State) (rtv []*State, isZero bool) {
 
 // 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) {
+func match(start *State, str string) (indices []matchIndex) {
+	return matchHelper(start, str, make([]matchIndex, 0), 0)
+}
+func matchHelper(start *State, str string, indices []matchIndex, offset int) []matchIndex {
+	// 'Base case' - exit if string is empty
+	if len(str) == 0 {
+		return indices
+	}
+
+	startIdx := 0
+	endIdx := 0
 	currentStates := make([]*State, 0)
 	tempStates := make([]*State, 0) // Used to store states that should be used in next loop iteration
 	i := 0                          // Index in string
@@ -28,12 +44,12 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 		for i < len(str) && int(str[i]) != start.content {
 			i++
 		}
+		startIdx = i
 		i++ // Advance to next character (if we aren't at a 0-state, which doesn't match anything), so that we can check for transitions. If we advance at a 0-state, we will never get a chance to match the first character
 	}
 	// TODO - If start state is kleene star, try to match the next state
 
 	currentStates = append(currentStates, start)
-	startIdx = i
 
 	// Main loop
 	for i < len(str) {
@@ -57,8 +73,10 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 				// This enables the 'greedy' behavior - last-state status is only checked if we can't match anything else
 				if state.isLast {
 					endIdx = i
-					return startIdx, endIdx, true
+					indices = append(indices, matchIndex{startIdx + offset, endIdx + offset})
 				}
+				// Recursion - match with rest of string
+				return matchHelper(start, str[i:], indices, offset+i)
 			}
 		}
 		currentStates = make([]*State, len(tempStates))
@@ -80,12 +98,10 @@ func match(start *State, str string) (startIdx int, endIdx int, matched bool) {
 	for _, state := range currentStates {
 		if state.isLast {
 			endIdx = i
-			return startIdx, endIdx, true
-		} else {
-			return -1, -1, false
+			indices = append(indices, matchIndex{startIdx + offset, endIdx + offset})
 		}
 	}
 
 	// Default
-	return -1, -1, false
+	return indices
 }