Wrote function to provide correct node for escaped character

postfixNode.go

@@ -1,16 +1,18 @@
 package main
 
+import "slices"
+
 type NodeType int
 
 // This is a list of the possible node types
 const (
 	CHARACTER NodeType = iota
-
 	PIPE
 	CONCATENATE
 	KLEENE
 	QUESTION
 	PLUS
+	ASSERTION
 )
 
 // This represents a node in the postfix representation of the expression
@@ -19,6 +21,41 @@ type postfixNode struct {
 	contents []rune // Contents of the node - the length of this would only be >1 if the node represents a character class
 }
 
+// Creates a new escaped node - the given character is assumed to have been preceded by a backslash
+func newEscapedNode(c rune) postfixNode {
+	toReturn := postfixNode{}
+	switch c {
+	case 's': // Whitespace
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, whitespaceChars...)
+	case 'S': // Non-whitespace - I am doing this in a fancy way, generating all dot characters, then removing whitespace characters from it
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool {
+			return slices.Contains(whitespaceChars, r)
+		})...)
+	case 'd': // Digits
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, digitChars...)
+	case 'D': // Non-digits - same fancy way as 'S'
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool {
+			return slices.Contains(digitChars, r)
+		})...)
+	case 'w': // word character
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, wordChars...)
+	case 'W': // Non-word character - same fancy way as 'S' and 'D'
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, slices.DeleteFunc(dotChars(), func(r rune) bool {
+			return slices.Contains(wordChars, r)
+		})...)
+	default: // None of the above - append it as a regular character
+		toReturn.nodetype = CHARACTER
+		toReturn.contents = append(toReturn.contents, c)
+	}
+	return toReturn
+}
+
 // Creates and returns a postfixNode based on the given contents
 func newPostfixNode(contents ...rune) postfixNode {
 	if len(contents) < 1 {