Initial import

expression_node.h

@@ -0,0 +1,22 @@
+#ifndef EXPRESSION_NODE_H
+#define EXPRESSION_NODE_H
+
+#include "tree_node.h"
+
+class TreePool;
+
+class ExpressionNode : public TreeNode {
+public:
+  ExpressionNode(int identifier) : TreeNode(identifier) {}
+
+  static TreePool * Pool() {
+    static TreePool pool;
+    return &pool;
+  }
+
+  virtual float approximate() = 0;
+  int numberOfOperands() { return numberOfChildren(); }
+  ExpressionNode * operand(int i) { return static_cast<ExpressionNode *>(childAtIndex(i)); }
+};
+
+#endif