lib/ordered_tree: add `parent`, `has` and `length`

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/lib/ordered_tree.nit b/lib/ordered_tree.nit
index 7216474..0b1d383 100644 (file)
--- a/lib/ordered_tree.nit
+++ b/lib/ordered_tree.nit
@@ -70,17 +70,47 @@ class OrderedTree[E: Object]
        # For each element, the ordered array of its direct sub-elements.
        var sub = new HashMap[E, Array[E]]
 
+       # The parent of each element.
+       #
+       # Roots have `null` as parent.
+       private var parents = new HashMap[E, nullable E]
+
+       redef fun length do return parents.length
+
+       redef fun has(e) do return parents.has_key(e)
+
+       # The parent of the element `e`
+       #
+       # Roots have `null` as parent.
+       #
+       # ~~~
+       # var tree = new OrderedTree[Int]
+       # tree.add(1, 2)
+       # assert tree.parent(2) == 1
+       # assert tree.parent(1) == null
+       # ~~~
+       fun parent(e: E): nullable E do return parents[e]
+
        # Add a new element `e` in the tree.
+       #
        # `p` is the parent of `e`.
-       # if `p` is null, then `e` is a root element.
+       # If `p` is null, then `e` is a root element.
+       #
+       # If `e` is already in the tree, it is detached from its old
+       # parent and attached to the new parent `p`.
        fun add(p: nullable E, e: E)
        do
+               detach(e)
+               parents[e] = p
                if p == null then
                        roots.add(e)
-               else if sub.has_key(p) then
-                       sub[p].add(e)
                else
-                       sub[p] = [e]
+                       if not has(p) then add(null, p)
+                       if sub.has_key(p) then
+                               sub[p].add(e)
+                       else
+                               sub[p] = [e]
+                       end
                end
        end
 
@@ -90,6 +120,20 @@ class OrderedTree[E: Object]
                for e in es do add(p, e)
        end
 
+       # Temporary remove `e`.
+       #
+       # Children of `e` are left untouched in the tree.
+       # This make the tree inconstant until `e` is added back.
+       private fun detach(e: E)
+       do
+               var old_parent = parents.get_or_null(e)
+               if old_parent != null then
+                       sub[old_parent].remove(e)
+               else if roots.has(e) then
+                       roots.remove(e)
+               end
+       end
+
        # print the full tree on `o`
        # Write a ASCII-style tree and use the `display` method to label elements
        redef fun write_to(stream: Writer)