X-Git-Url: http://nitlanguage.org

diff --git a/lib/trees/abstract_tree.nit b/lib/trees/abstract_tree.nit
index 38d22e4..dccde3a 100644
--- a/lib/trees/abstract_tree.nit
+++ b/lib/trees/abstract_tree.nit
@@ -36,10 +36,16 @@ abstract class TreeMap[K: Comparable, E]
 	fun show_dot is abstract
 end
 
-# Node used in Tree implementation
-# nodes are used to store values
-# * `E`: type of value
-class TreeNode[K: Comparable, E]
+# Abstract node structure used in `Tree` implementation
+#
+# Nodes are defined recursively each node (except the root one) pointing to a parent.
+# Nodes can be used to store data with the `TreeNode::value` attribute.
+#
+# Formal parameters:
+# * `K`: key type (a `Comparable` one so nodes can be sorted by their keys)
+# * `E`: value type (to store your data)
+abstract class TreeNode[K: Comparable, E]
+	super Comparable
 
 	# TreeNode type
 	type N: TreeNode[K, E]
@@ -50,17 +56,44 @@ class TreeNode[K: Comparable, E]
 	# `value` stored in the node
 	var value: E
 
-	# Direct parent of this node (null if the node is root)
+	# Direct parent of this node (`null` if the node is root)
+	#
+	# See `Tree::root`.
 	var parent: nullable N = null is writable
 
+	# Depth in tree (length of the path from `self` to `root`)
+	fun depth: Int do
+		var node = parent
+		var i = 0
+		while node != null do
+			node = node.parent
+			i += 1
+		end
+		return i
+	end
+
 	redef fun to_s do return "\{{value or else ""}\}"
 
 	# Return dot representation of this node
-	# Used for debugging by `AbstractTree::show_dot`
+	#
+	# See `Tree::show_dot`.
 	fun to_dot: String do
 		var res = new FlatBuffer
 		res.append "\"{self}\";\n"
 		if parent != null then res.append "\"{parent.as(not null)}\" -> \"{self}\"[dir=back];\n"
 		return res.to_s
 	end
+
+	redef type OTHER: N
+
+	# Nodes equality is done on `value` equality
+	#
+	# Redefine this method to change the default behavior.
+	redef fun ==(o) do
+		if not o isa N then return false
+		return self.value == o.value
+	end
+
+	# Nodes ordering is based on the `key`
+	redef fun <(o) do return self.key < o.key
 end