From 444413e1f75a69b1dd86547d04a1ae94cd81f9e6 Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Mon, 28 Oct 2024 17:39:32 -0400
Subject: [PATCH] Added postfixNode type to represent a node in the postfix
 representation of the regex

---
 postfixNode.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 postfixNode.go

diff --git a/postfixNode.go b/postfixNode.go
new file mode 100644
index 0000000..c7f384a
--- /dev/null
+++ b/postfixNode.go
@@ -0,0 +1,49 @@
+package main
+
+type NodeType int
+
+// This is a list of the possible node types
+const (
+	CHARACTER NodeType = iota
+
+	PIPE
+	CONCATENATE
+	KLEENE
+	QUESTION
+	PLUS
+)
+
+// 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
+}
+
+// Creates and returns a postfixNode based on the given contents
+func newPostfixNode(contents ...rune) postfixNode {
+	if len(contents) < 1 {
+		panic("Empty node.")
+	}
+	to_return := postfixNode{}
+	if len(contents) > 1 { // If the node has more than element, it must be a character class - the type must be CHARACTER
+		to_return.nodetype = CHARACTER
+		to_return.contents = contents
+	} else { // Node has one element, could be anything
+		switch contents[0] {
+		case '+':
+			to_return.nodetype = PLUS
+		case '?':
+			to_return.nodetype = QUESTION
+		case '*':
+			to_return.nodetype = KLEENE
+		case '|':
+			to_return.nodetype = PIPE
+		case CONCAT:
+			to_return.nodetype = CONCATENATE
+		default:
+			to_return.nodetype = CHARACTER
+		}
+		to_return.contents = append(to_return.contents, contents...)
+	}
+	return to_return
+}