1 files changed, 13 insertions, 1 deletions
diff --git a/tree.h b/tree.h
index a58d270..8353a6d 100644
--- a/tree.h
+++ b/tree.h
@@ -1,3 +1,6 @@
+#ifndef TREE_H_HG
+#define TREE_H_HG
+
 enum nodeType {
   BIOP,
   UNOP,
@@ -7,7 +10,16 @@ enum nodeType {
 typedef struct node {
   enum nodeType type;
   char el;
-  struct node *child[2];
+	union {
+		struct node *child[2];
+		struct {
+			struct node *lhs, *rhs;
+		};
+		struct node *value;
+	};
 } node;
+
 node * parse(char *str);
 void printTree(node *root, int level);
+
+#endif