1 files changed, 14 insertions, 11 deletions
diff --git a/chain/src/item/mod.rs b/chain/src/item/mod.rs
index 5efa710..54ca946 100644
--- a/chain/src/item/mod.rs
+++ b/chain/src/item/mod.rs
@@ -32,8 +32,9 @@ use core::borrow::Borrow;
 /// Also this might be empty if it represents the root node.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Default)]
 pub enum PaVi {
-    /// An edge from a node, as the n-th child.
-    Parent(usize, usize),
+    /// An edge from a node, as the n-th child, along with the
+    /// nth-child node number.
+    Parent(usize, usize, usize),
     /// A virtual segment from a non-terminal by a terminal, rooted at
     /// a node.
     ///
@@ -50,16 +51,12 @@ pub enum PaVi {
     Empty,
 }
 
-impl From<Parent> for PaVi {
-    fn from(value: Parent) -> Self {
-        Self::Parent(value.node(), value.edge())
-    }
-}
-
-impl core::fmt::Display for PaVi {
+impl std::fmt::Display for PaVi {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::Parent(node, edge) => write!(f, "the {edge}-th edge from {node}"),
+            Self::Parent(node, edge, child) => {
+                write!(f, "the {edge}-th edge from {node} to {child}")
+            }
             Self::Virtual(nt, t, node) => write!(
                 f,
                 "a virtual node for non-terminal {nt} and terminal {t} at node {node}"
@@ -72,13 +69,17 @@ impl core::fmt::Display for PaVi {
 impl PaVi {
     /// Get the Parent variant.
     fn parent(self) -> Option<Parent> {
-        if let Self::Parent(node, edge) = self {
+        if let Self::Parent(node, edge, _) = self {
             Some(Parent::new(node, edge))
         } else {
             None
         }
     }
 
+    fn is_virtual(self) -> bool {
+        matches!(self, Self::Virtual(_, _, _))
+    }
+
     /// Is this an empty segment?
     fn is_empty(self) -> bool {
         self == Self::Empty
@@ -290,3 +291,5 @@ pub mod default;
 pub mod genins;
 
 pub use genins::generate_fragment;
+
+pub mod reduction;