From 8f9cfd5cc9d20064b6a59587343322ebbc9830da Mon Sep 17 00:00:00 2001
From: Stefan O'Rear <stefanor@cox.net>
Date: Tue, 31 Aug 2010 11:21:31 -0700
Subject: [PATCH] [nrx] Simplify xact/backtrack correspondence

---
 lib/Cursor.cs | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/lib/Cursor.cs b/lib/Cursor.cs
index 7f9719d1..1f68a464 100644
--- a/lib/Cursor.cs
+++ b/lib/Cursor.cs
@@ -47,7 +47,7 @@ public struct State {
 
         public XAct xact;
     }
-    // invariant: xact of top state is NEVER committed
+    // invariant: xact of top state is NEVER committed/pruned
 
     public PSN<State> bt;
 
@@ -68,7 +68,7 @@ public struct State {
     public Frame Backtrack(Frame th) {
         do {
             bt = bt.next;
-        } while (bt != null && bt.obj.xact.committed);
+        } while (bt != null && (bt.obj.xact.committed || bt.obj.ip < 0));
         if (bt == null) {
             return th.caller;
         } else {
@@ -80,10 +80,6 @@ public struct State {
     public void PushBacktrack(string name, int ip) {
         bt.obj.ip = ip;
         bt = new PSN<State>(bt.obj, bt);
-        PushMark(name);
-    }
-
-    public void PushMark(string name) {
         bt.obj.xact = new XAct(name, bt.obj.xact);
     }