Added lookaround-related fields to postfixNode struct

postfixNode.go

@@ -15,15 +15,23 @@ const (
 	RPAREN
 )
 
+// Helper constants for lookarounds
+const POSITIVE = 1
+const NEGATIVE = -1
+const LOOKAHEAD = 1
+const LOOKBEHIND = -1
+
 var INFINITE_REPS int = -1 // Represents infinite reps eg. the end range in {5,}
 // This represents a node in the postfix representation of the expression
 type postfixNode struct {
 	nodetype       NodeType
-	contents  []rune // Contents of the node - the length of this would only be >1 if the node represents a character class
+	contents       []rune // Contents of the node
 	startReps      int    // Minimum number of times the node should be repeated - used with numeric specifiers
 	endReps        int    // Maximum number of times the node should be repeated - used with numeric specifiers
 	allChars       bool   // Whether or not the current node represents all characters (eg. dot metacharacter)
 	except         []rune // For inverted character classes, we match every unicode character _except_ a few. In this case, allChars is true and the exceptions are placed here.
+	lookaroundSign int    // ONLY USED WHEN nodetype == ASSERTION. Whether we have a positive or negative lookaround.
+	lookaroundDir  int    // Lookbehind or lookahead
 }
 
 // Creates a new escaped node - the given character is assumed to have been preceded by a backslash