forest seems to be completed

I seem to have finished the implementation of forests.  Now it remains
the implementation of the chain-rule machine, of which I have a rough
plan now.

1 files changed, 18 insertions, 0 deletions

diff --git a/graph/src/lib.rs b/graph/src/lib.rs
index 6813df3..6af7889 100644
--- a/graph/src/lib.rs
+++ b/graph/src/lib.rs
@@ -23,6 +23,7 @@ pub use adlist::ALGraph;
 pub mod labelled;
 
 pub use labelled::DLGraph;
+pub use labelled::PLGraph;
 
 pub mod builder;
 
@@ -252,6 +253,23 @@ pub trait ParentsGraph: Graph {
     fn parents_of(&self, node_id: usize) -> Result<<Self as ParentsGraph>::Iter<'_>, Error>;
 }
 
+// TODO: Design a trait of graphs which can "replace" a certain child
+// by another child.  To re-direct children, so to speak.
+
+/// An /exended/ graph in the sense that it offers the ability to
+/// "redirect" children of a node to another node.
+pub trait RedirectGraph: Graph {
+    /// Replace the edge that points from `node_id` to the
+    /// `child_index`-th child by a new edge that points to
+    /// `new_child`.
+    fn redirect(
+        &mut self,
+        node_id: usize,
+        child_index: usize,
+        new_child: usize,
+    ) -> Result<(), Error>;
+}
+
 /// A labelled graph is just a graph with labels associated to
 /// vertices and / or edges.
 ///