Added the functionality of split or clone.

I need more than the ability to clone nodes: I also need to split the
nodes.  Now this seems to be correctly added.

1 files changed, 38 insertions, 18 deletions

diff --git a/chain/src/item/mod.rs b/chain/src/item/mod.rs
index c614802..284d640 100644
--- a/chain/src/item/mod.rs
+++ b/chain/src/item/mod.rs
@@ -5,16 +5,6 @@
 //! More specifically, it implements the iten derivation forests for
 //! the machine.
 
-// TODO: Implement an enumeration for Parent or Segment, perhaps
-// called PaSe.
-
-// TODO: Move functions for handling forests, currently contained
-// within the method derive to this module, and make them aware of the
-// enumeration PaSe.
-
-// TODO: Implement the Item trait from semirings for the item
-// derivation forest, and then we can easily execute items later on.
-
 use graph::{error::Error as GError, GraphLabel, LabelGraph, Parent, ParentsGraph};
 
 use core::borrow::Borrow;
@@ -88,7 +78,7 @@ impl core::fmt::Display for ForestLabelType {
         match self {
             Self::Packed => write!(f, "packed"),
             Self::Plain => write!(f, "plain"),
-            Self::Cloned(index) => write!(f, "the {index}-th clone"),
+            Self::Cloned(index) => write!(f, "clone({index})"),
         }
     }
 }
@@ -102,7 +92,11 @@ pub struct ForestLabel<T: GraphLabel> {
 
 impl<T: GraphLabel> core::fmt::Display for ForestLabel<T> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        writeln!(f, "label: {}, status: {}", self.label, self.status)
+        if !matches!(self.status, ForestLabelType::Plain) {
+            write!(f, "{}, {}", self.label, self.status)
+        } else {
+            write!(f, "{}", self.label)
+        }
     }
 }
 
@@ -128,6 +122,10 @@ impl core::fmt::Display for ForestLabelError {
 impl std::error::Error for ForestLabelError {}
 
 impl<T: GraphLabel> ForestLabel<T> {
+    fn new(label: T, status: ForestLabelType) -> Self {
+        Self { label, status }
+    }
+
     /// Retrieve the label.
     pub fn label(&self) -> T {
         self.label
@@ -135,7 +133,7 @@ impl<T: GraphLabel> ForestLabel<T> {
 
     /// Return true if and only if this node is packed.
     pub fn is_packed(&self) -> bool {
-        matches!(self.status, ForestLabelType::Packed)
+        self.status == ForestLabelType::Packed
     }
 
     /// Retrieve the optional clone index.
@@ -146,12 +144,18 @@ impl<T: GraphLabel> ForestLabel<T> {
         }
     }
 
+    /// Return true if and only if this node is a plain node.
+    pub fn is_plain(&self) -> bool {
+        self.status == ForestLabelType::Plain
+    }
+
     /// Try to clone a node.
     pub fn clone<F>(self, forest: &F) -> Result<Self, ForestLabelError>
     where
-        F: Forest<T>,
+        F: LabelGraph<ForestLabel<T>>,
     {
         if self.is_packed() {
+            dbg!();
             Err(ForestLabelError::ClonePack)
         } else {
             let clone_index = if let Some(old_index) = self.clone_index() {
@@ -221,6 +225,13 @@ pub trait Forest<T: GraphLabel>: ParentsGraph + LabelGraph<ForestLabel<T>> {
     /// label.
     fn new_leaf(label: T) -> Self;
 
+    /// Transform the label at the given node.
+    fn transform_label(
+        &mut self,
+        node_id: usize,
+        transform: impl FnOnce(T) -> T,
+    ) -> Result<(), Self::Error>;
+
     /// Detect if the fragment is a prefix of the sub-forest rooted at
     /// `node_id`.
     fn is_prefix<F>(&self, node_id: usize, fragment: F) -> Result<bool, Self::Error>
@@ -235,13 +246,22 @@ pub trait Forest<T: GraphLabel>: ParentsGraph + LabelGraph<ForestLabel<T>> {
     /// Clone a node by making a new node and making all the nodes
     /// that previously pointed to the old node now point to the new
     /// node, and the new node points to the old node.  Return the
-    /// index of the new node.  In addition, if the old node had
-    /// already been cloned, just return the index of its
-    /// representative.
+    /// index of the new node.  However, if, and only if,
+    /// `no_new_clone` is `true`, do not make a new clone; instead
+    /// return the clone index that would be used if a new clone was
+    /// made.
+    ///
+    /// Also, `preserved_edges_num` many edges out of the old node
+    /// will be copied to be the children of the new node.
     ///
     /// The labels of the representing node and of the cloned node
     /// will be handled automatically.
-    fn clone_node(&mut self, node_id: usize) -> Result<usize, Self::Error>;
+    fn clone_node(
+        &mut self,
+        node_id: usize,
+        preserved_edges_num: usize,
+        no_new_clone: bool,
+    ) -> Result<usize, Self::Error>;
 }
 
 pub mod default;