Wrote a simplified regular expression parser to make life easier (it only does single matches; i.e., no one-or-more matches, etc.).

Fixed some of the whitespace/line break matching.

scanner.h

@@ -5,22 +5,49 @@
 #include <queue>
 #include <stack>
 #include <set>
+#include "regex.h"
 
 namespace YAML
 {
 	class Token;
 
+	namespace Exp
+	{
+		// misc
+		const RegEx Blank = RegEx(' ') || RegEx('\t');
+		const RegEx Break = RegEx('\n');
+		const RegEx BlankOrBreak = Blank || Break;
+
+		// actual tags
+
+		const RegEx DocStart = RegEx("---") + (BlankOrBreak || RegEx(EOF) || RegEx());
+		const RegEx DocEnd = RegEx("...") + (BlankOrBreak || RegEx(EOF) || RegEx());
+		const RegEx BlockEntry = RegEx('-') + (BlankOrBreak || RegEx(EOF));
+		const RegEx Key = RegEx('?'),
+		            KeyInFlow = RegEx('?') + BlankOrBreak;
+		const RegEx Value = RegEx(':'),
+		            ValueInFlow = RegEx(':') + BlankOrBreak;
+		const RegEx Comment = RegEx('#');
+
+		// Plain scalar rules:
+		// . Cannot start with a blank.
+		// . Can never start with any of , [ ] { } # & * ! | > \' \" % @ `
+		// . In the block context - ? : must be not be followed with a space.
+		// . In the flow context ? : are illegal and - must not be followed with a space.
+		const RegEx PlainScalar = !(BlankOrBreak || RegEx(",[]{}#&*!|>\'\"%@`", REGEX_OR) || (RegEx("-?:") + Blank)),
+	                PlainScalarInFlow = !(BlankOrBreak || RegEx("?:,[]{}#&*!|>\'\"%@`", REGEX_OR) || (RegEx('-') + Blank));
+		const RegEx IllegalColonInScalar = RegEx(':') + !BlankOrBreak;
+		const RegEx EndScalar = RegEx(':') + BlankOrBreak,
+		            EndScalarInFlow = (RegEx(':') + BlankOrBreak) || RegEx(",:?[]{}");
+	}
+
 	namespace Keys
 	{
-		const char Comment = '#';
 		const char FlowSeqStart = '[';
 		const char FlowSeqEnd = ']';
 		const char FlowMapStart = '{';
 		const char FlowMapEnd = '}';
 		const char FlowEntry = ',';
-		const char BlockEntry = '-';
-		const char Key = '?';
-		const char Value = ':';
 		const char Alias = '*';
 		const char Anchor = '&';
 		const char Tag = '!';
@@ -49,8 +76,6 @@ namespace YAML
 		void EatLineBreak();
 
 		bool IsWhitespaceToBeEaten(char ch);
-		bool IsLineBreak(char ch);
-		bool IsBlank(char ch);
 		bool IsDocumentStart();
 		bool IsDocumentEnd();
 		bool IsBlockEntry();