Fixed inverted Perl classes inside character classes eg. '[\D]'; added new flag for 'single-line' mode, where dot metacharacter matches newlines

compile.go

@@ -24,9 +24,10 @@ const CONCAT rune = '~'
 type ReFlag int
 
 const (
-	RE_NO_FLAGS ReFlag = iota
+	RE_NO_FLAGS         ReFlag = iota
-	RE_CASE_INSENSITIVE
+	RE_CASE_INSENSITIVE        // Case insensitive matching
-	RE_MULTILINE
+	RE_MULTILINE               // '^' and '$' assert at start and end of _line_, rather than start and end of input string
+	RE_SINGLE_LINE             // Dot metacharacter matches newline characters.
 )
 
 func isOperator(c rune) bool {
@@ -78,6 +79,8 @@ func getPOSIXClass(str []rune) (bool, string) {
 var caseInsensitive bool
 
 // Stores whether the multiline flag has been enabled.
+// In multi-line mode, '^' and '$' assert position at the start and
+// end of a _line_ rather than the entire input.
 var multilineMode bool
 
 /*
@@ -93,10 +96,10 @@ func shuntingYard(re string, flags ...ReFlag) ([]postfixNode, error) {
 
 	caseInsensitive = false
 	multilineMode = false
-	// In Multiline mode, the newline character is considered a
-	// 'dot' character ie. the dot metacharacter matches a newline as well.
 	if slices.Contains(flags, RE_MULTILINE) {
 		multilineMode = true
+	}
+	if slices.Contains(flags, RE_SINGLE_LINE) {
 		notDotChars = []rune{}
 	} else {
 		notDotChars = []rune{'\n'}
@@ -965,6 +968,12 @@ func thompson(re []postfixNode) (Reg, error) {
 					})...)
 				}
 				s.content = rune2Contents(nodeContents)
+				if len(node.except) > 0 {
+					s.allChars = true
+					s.except = slices.Concat(Map(node.except, func(n postfixNode) []rune {
+						return n.contents
+					})...)
+				}
 				return &s
 			})
 			// Reduce the list of states down to a single state by alternating them