Added flag to print match indices, and to enable multi-line mode

main.go

@@ -126,7 +126,7 @@ func shuntingYard(re string) []postfixNode {
 		6. If current character is '{', find the appropriate numeric specifier (range start, range end). Apply the range to the postfixNode at the end of outQueue.
 		*/
 		c := re_postfix[i]
-		if isAlphaNum(c) {
+		if isNormalChar(c) {
 			outQueue = append(outQueue, newPostfixNode(c))
 			continue
 		}
@@ -379,7 +379,9 @@ func main() {
 	// 1. Without '-v': Prints only matches. Prints a newline after every match.
 	// 2. With '-v': Substitutes all matches with empty string.
 	onlyFlag := flag.Bool("o", false, "Print only colored content. Overrides -l.")
-	lineFlag := flag.Bool("l", false, "Only print lines with a match (or with no matches, if -v is enabled")
+	lineFlag := flag.Bool("l", false, "Only print lines with a match (or with no matches, if -v is enabled (similar to grep's default")
+	multiLineFLag := flag.Bool("t", false, "Multi-line mode. Treats newline just like any character.")
+	printMatchesFlag := flag.Bool("p", false, "Prints start and end index of each match. Can only be used with '-t' for multi-line mode.")
 	flag.Parse()
 
 	// -l and -o are mutually exclusive: -o overrides -l
@@ -402,16 +404,50 @@ func main() {
 	var test_str string
 	var test_runes []rune // Rune-slice representation of test_str
 	var err error
-	// Create reader for stdin and writer for stdout // End index is one more than last index of match
+	var linesRead bool // Whether or not we have read the lines in the file
+	// Create reader for stdin and writer for stdout
 	reader := bufio.NewReader(os.Stdin)
 	out := bufio.NewWriter(os.Stdout)
 
 	re_postfix := shuntingYard(re)
 	startState := thompson(re_postfix)
-	// Read every string from stdin until we encounter an error. If the error isn't EOF, panic.'
-	for test_str, err = reader.ReadString('\n'); err == nil; test_str, err = reader.ReadString('\n') {
+	for true {
+		if linesRead {
+			break
+		}
+		if !(*multiLineFLag) {
+			// Read every string from stdin until we encounter an error. If the error isn't EOF, panic.
+			test_str, err = reader.ReadString('\n')
+			if err != nil {
+				if err == io.EOF {
+					linesRead = true
+				} else {
+					panic(err)
+				}
+			}
+		} else {
+			// Multi-line mode - read every line of input into a temp. string.
+			// test_str will contain all lines of input (including newline characters)
+			// as one string.
+			var temp string
+			for temp, err = reader.ReadString('\n'); err == nil; temp, err = reader.ReadString('\n') {
+				test_str += temp
+			}
+			// Assuming err != nil
+			if err == io.EOF {
+				linesRead = true
+			} else {
+				panic(err)
+			}
+		}
 		test_runes = []rune(test_str)
 		matchIndices := findAllMatches(startState, []rune(test_runes))
+		if *printMatchesFlag {
+			for _, idx := range matchIndices {
+				fmt.Printf("%s\n", idx.toString())
+			}
+			continue
+		}
 		// Decompose the array of matchIndex structs into a flat unique array of ints - if matchIndex is {4,7}, flat array will contain 4,5,6
 		// This should make checking O(1) instead of O(n)
 		indicesToPrint := new_uniq_arr[int]()
@@ -463,7 +499,4 @@ func main() {
 			panic(err)
 		}
 	}
-	if err != io.EOF {
-		panic(err)
-	}
 }