diff --git a/addition_node.h b/addition_node.h
index e60f2143b..b03278a70 100644
--- a/addition_node.h
+++ b/addition_node.h
@@ -17,8 +17,8 @@ public:
   }
   float approximate() override {
     float result = 0.0f;
-    for (int i=0; i<numberOfOperands(); i++) {
-      result += operand(i)->approximate();
+    for (int i=0; i<numberOfChildren(); i++) {
+      result += child(i)->approximate();
     }
     return result;
   }
diff --git a/expression_node.h b/expression_node.h
index 7cd7bdffd..433bb5ce7 100644
--- a/expression_node.h
+++ b/expression_node.h
@@ -5,13 +5,8 @@
 
 class ExpressionNode : public TreeNode {
 public:
-  ExpressionNode() : TreeNode(TreePool::sharedPool()->generateIdentifier()) {
-    TreePool::sharedPool()->registerNode(this);
-  }
-
   virtual float approximate() = 0;
-  int numberOfOperands() { return numberOfChildren(); }
-  ExpressionNode * operand(int i) { return static_cast<ExpressionNode *>(childAtIndex(i)); }
+  ExpressionNode * child(int i) { return static_cast<ExpressionNode *>(treeChildAtIndex(i)); }
 };
 
 #endif
diff --git a/tree_node.h b/tree_node.h
index 0a0cdfc9d..f94978c70 100644
--- a/tree_node.h
+++ b/tree_node.h
@@ -100,7 +100,7 @@ public:
     return 0;
   }
 
-  TreeNode * childAtIndex(int i) const {
+  TreeNode * treeChildAtIndex(int i) const {
     assert(i >= 0);
     assert(i < numberOfChildren());
     TreeNode * child = next();