From 83e69a4872a2c583090e877e636208c1fd068744 Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Wed, 25 Aug 2021 12:56:56 +0200
Subject: [PATCH] rulegen:: addstep used in one more place

---
 rulegen.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/rulegen.cpp b/rulegen.cpp
index 068b5299..0389d6f9 100644
--- a/rulegen.cpp
+++ b/rulegen.cpp
@@ -152,6 +152,7 @@ EX void ufindc(tcell*& c) {
 
 EX tcell *first_tcell = nullptr;
 
+// sometimes the standard x+wstep returns nullptr because of unification
 twalker addstep(twalker x) {
   x.cpeek();
   ufind(x);
@@ -872,12 +873,12 @@ EX set<tcell*> single_live_branch_close_to_root;
 
 void treewalk(twalker& cw, int delta) {
   int d = get_parent_dir(cw.at);
-  if(cw.spin == d) cw += wstep;
+  if(cw.spin == d) cw = addstep(cw);
   else {
     auto cw1 = addstep(cw);
     get_parent_dir(cw1.at);
     ufind(cw1);
-    if(get_parent_dir(cw1.at) == cw1.spin) cw += wstep;
+    if(get_parent_dir(cw1.at) == cw1.spin) cw = cw1;
     }
   cw+=delta;
   }