Fix a bug of using incorrect forest nodes to plant.

Previously some incorrect forest nodes will be used for planting new
nodes.  I cannot fix the root cause of their presence in the
chain-rule machine.  But I can ignore them when they are encountered.

Of course I would like to really prevent them from existing, but still
cannot figure out how.

3 files changed, 31 insertions, 8 deletions

diff --git a/chain/src/default.rs b/chain/src/default.rs
index 1e0eba2..11f0c93 100644
--- a/chain/src/default.rs
+++ b/chain/src/default.rs
@@ -633,6 +633,7 @@ impl Chain for DefaultChain {
                             let mut new_label = *child_label;
 
                             new_label.set_true_source(true_pavi);
+                            // new_label.set_forest_source(pavi);
 
                             output.extend(
                                 std::iter::repeat(new_label.into())
@@ -723,6 +724,20 @@ impl Chain for DefaultChain {
                             continue;
                         }
 
+                        #[allow(clippy::single_match)]
+                        match label.forest_source() {
+                            PaVi::Parent(node, _, _) => match self.forest.vertex_label(node) {
+                                Ok(Some(label)) => match label.label().end() {
+                                    Some(end) if end != pos => {
+                                        continue;
+                                    }
+                                    _ => {}
+                                },
+                                _ => {}
+                            },
+                            _ => {}
+                        }
+
                         let virtual_node = self
                             .atom
                             .atom(non, t)
@@ -911,7 +926,7 @@ impl Chain for DefaultChain {
 
         // First perform reduction.
 
-        let _ = self.forest.print_viz("forest before reduction.gv");
+        // let _ = self.forest.print_viz("forest before reduction.gv");
 
         // self.forest.reduction(root, pos, ter, &self.atom, true)?;
 
@@ -1070,7 +1085,7 @@ impl Chain for DefaultChain {
         self.atom.print_virtual();
         let _ = item::default::print_labels(&self.atom, &self.forest);
 
-        let _ = self.forest.print_viz("forest before extraction.gv");
+        // let _ = self.forest.print_viz("forest before extraction.gv");
 
         result = self.forest.extract(pos)?;
 
diff --git a/chain/src/item/genins.rs b/chain/src/item/genins.rs
index 262728f..e3e79b6 100644
--- a/chain/src/item/genins.rs
+++ b/chain/src/item/genins.rs
@@ -212,7 +212,7 @@ impl DefaultForest<ForestLabel<GrammarLabel>> {
         // Whether or not to print detailed graphs of each step of
         // operation for debugging purposes.
         let mut to_print = false;
-        // let mut to_print = (8..=10).contains(&pos);
+        // let mut to_print = (11..=12).contains(&pos);
 
         if std::fs::metadata("output/").is_err() {
             to_print = false;
@@ -419,8 +419,8 @@ impl DefaultForest<ForestLabel<GrammarLabel>> {
                 .collect();
         }
 
-        // if pos == 9 {
-        //     dbg!(&parents);
+        // if pos == 12 {
+        //     dbg!(num, &parents, pavi, label);
         // }
 
         let mut non_empty = false;
@@ -535,7 +535,6 @@ impl DefaultForest<ForestLabel<GrammarLabel>> {
                     parents,
                     reduction_info,
                     atom.query_reduction(label.label(), atom_child).unwrap(),
-                    is_empty_segment,
                     atom.trace(0, 3, atom_child)
                         .into_iter()
                         .flatten()
@@ -616,6 +615,10 @@ impl DefaultForest<ForestLabel<GrammarLabel>> {
                 unreachable!("the forest is wrongly planted");
             }
 
+            // if pos == 11 {
+            //     dbg!(root_label, node, edge, child);
+            // }
+
             // dbg!(node, edge, root_label, leaf_label);
             PaVi::Parent(node, edge, child)
         } else {
diff --git a/chain/src/lib.rs b/chain/src/lib.rs
index bf3a8b4..f16ebb2 100644
--- a/chain/src/lib.rs
+++ b/chain/src/lib.rs
@@ -61,8 +61,13 @@ impl Edge {
         self.forest_source
     }
 
-    /// Return the associated bottom edge of the edge from which
-    /// onwards we shall perform the reduction.
+    /// Set the associated forest edge of the edge of the edge.
+    pub fn set_forest_source(&mut self, source: PaVi) {
+        self.forest_source = source;
+    }
+
+    /// Set the associated bottom edge of the edge from which onwards
+    /// we shall perform the reduction.
     pub fn set_true_source(&mut self, true_source: PaVi) {
         self.true_source = true_source;
     }