1 files changed, 18 insertions, 0 deletions
diff --git a/chain/src/atom/mod.rs b/chain/src/atom/mod.rs
index 4b3bfce..1fdbbd1 100644
--- a/chain/src/atom/mod.rs
+++ b/chain/src/atom/mod.rs
@@ -35,6 +35,24 @@ pub trait Atom: Nfa<LabelType<TNT>> + Deref<Target = Grammar> {
 
     /// Return the bound for `is_accepting`.
     fn accepting_len(&self) -> usize;
+
+    /// Tell whether a node is accepting inside a frame of the
+    /// non-terminal `frame_nt`, that is to say, whether reaching the
+    /// node completes `frame_nt`.
+    ///
+    /// For a rule position this is not the same as `is_accepting`,
+    /// since the states are shared by all non-terminals.  For other
+    /// nodes, virtual nodes included, it is the same.
+    fn is_accepting_in(&self, frame_nt: usize, node_id: usize) -> Result<bool, GrammarError>;
+
+    /// Tell whether, inside a frame of the non-terminal `frame_nt`,
+    /// we are allowed to move into the node `node_id`.
+    ///
+    /// The states of the automaton are shared by all non-terminals,
+    /// so a rule position is allowed only if the non-terminal owning
+    /// it is a left corner of `frame_nt`.  Other nodes are always
+    /// allowed.
+    fn allowed_in_frame(&self, frame_nt: usize, node_id: usize) -> bool;
 }
 
 pub mod default;