Added case-insensitve flag

main.go

@@ -16,6 +16,7 @@ import (
 const CONCAT rune = '~'
 
 var notDotChars []rune
+var caseInsensitiveFlag *bool // Whether we are running in case-insensitive mode
 
 func isOperator(c rune) bool {
 	if c == '+' || c == '?' || c == '*' || c == '|' || c == CONCAT {
@@ -155,7 +156,11 @@ func shuntingYard(re string) []postfixNode {
 		*/
 		c := re_postfix[i]
 		if isNormalChar(c) {
+			if *caseInsensitiveFlag {
+				outQueue = append(outQueue, newPostfixNode(allCases(c)...))
+			} else {
 				outQueue = append(outQueue, newPostfixNode(c))
+			}
 			continue
 		}
 		// Escape character
@@ -501,6 +506,7 @@ func main() {
 	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.")
+	caseInsensitiveFlag = flag.Bool("i", false, "Case-insensitive. Disregard the case of all characters.")
 	flag.Parse()
 
 	// In multi-line mode, 'dot' metacharacter also matches newline