diff --git a/tree_node.cpp b/tree_node.cpp
index e05cc7bc7..2499511e1 100644
--- a/tree_node.cpp
+++ b/tree_node.cpp
@@ -3,6 +3,9 @@
 #include "expression_node.h"
 
 TreeNode * TreeNode::treeParent() const {
+// Choose between those two algorithms: the first has complexity O(numberNodes) but uses 0(3maxNumberNodes) space
+// The second is much clearer for the reader and uses no space, but has complexity 0
+#if 0
   int cursor = -1;
   TreeNode * parentsHistory[TreePool::MaxNumberOfNodes];
   int numberOfChildrenHistory[TreePool::MaxNumberOfNodes];
@@ -29,6 +32,26 @@ TreeNode * TreeNode::treeParent() const {
   }
   assert(false);
   return nullptr;
+#else
+  for (TreeNode * node : TreePool::sharedPool()->allNodes()) {
+    if (node == this) {
+      return nullptr;
+    }
+    if (node->hasChild(this)) {
+      return node;
+    }
+  }
+  assert(false);
+  return nullptr;
+#endif
+}
+
+int TreeNode::numberOfDescendants(bool includeSelf) const {
+  int result = includeSelf ? 1 : 0;
+  for (TreeNode * child : depthFirstChildren()) {
+    result++;
+  }
+  return result;
 }
 
 TreeNode * TreeNode::treeChildAtIndex(int i) const {
diff --git a/tree_node.h b/tree_node.h
index d892f6829..74b413618 100644
--- a/tree_node.h
+++ b/tree_node.h
@@ -42,11 +42,13 @@ public:
   // Hierarchy
   TreeNode * treeParent() const;
   virtual int numberOfChildren() const { return 0; }
+  int numberOfDescendants(bool includeSelf) const;
   TreeNode * treeChildAtIndex(int i) const;
+  bool hasChild(const TreeNode * child) const;
 
   class Iterator {
     public:
-    Iterator(TreeNode * node) : m_node(node) {}
+    Iterator(const TreeNode * node) : m_node(const_cast<TreeNode *>(node)) {}
     TreeNode * operator*() { return m_node; }
     bool operator!=(const Iterator& it) const { return (m_node != it.m_node); }
   protected:
@@ -55,7 +57,7 @@ public:
 
   class Direct {
   public:
-    Direct(TreeNode * node) : m_node(node) {}
+    Direct(const TreeNode * node) : m_node(const_cast<TreeNode *>(node)) {}
     class Iterator : public TreeNode::Iterator {
     public:
       using TreeNode::Iterator::Iterator;
@@ -72,7 +74,7 @@ public:
 
   class DepthFirst {
   public:
-    DepthFirst(TreeNode * node) : m_node(node) {}
+    DepthFirst(const TreeNode * node) : m_node(const_cast<TreeNode *>(node)) {}
     class Iterator : public TreeNode::Iterator {
     public:
       using TreeNode::Iterator::Iterator;
@@ -87,8 +89,8 @@ public:
     TreeNode * m_node;
   };
 
-  Direct directChildren() { return Direct(this); }
-  DepthFirst depthFirstChildren() { return DepthFirst(this); }
+  Direct directChildren() const { return Direct(this); }
+  DepthFirst depthFirstChildren() const { return DepthFirst(this); }
 
   TreeNode * next() const {
     // Simple version would be "return this + 1;", with pointer arithmetics taken care of by the compiler.