From 8d5a358b3884cfe425dec2269763e1deb8e8a104 Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Fri, 6 Mar 2020 02:36:11 +0100
Subject: [PATCH] reg3:: added celldistance_534

---
 reg3.cpp | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/reg3.cpp b/reg3.cpp
index 11c0aed5..2c0e9321 100644
--- a/reg3.cpp
+++ b/reg3.cpp
@@ -1254,10 +1254,55 @@ EX int quotient_count() {
   return isize(regmap()->quotient_map->allh);
   }
 
+/** This is a generalization of hyperbolic_celldistance in expansion.cpp to three dimensions.
+    It still assumes that there are at most 4 cells around every edge, and that distances from
+    the origin are known, so it works only in {5,3,4}.
+ */
+
+int celldistance_534(cell *c1, cell *c2) {
+  int d1 = celldist(c1);
+  int d2 = celldist(c2);
+
+  vector<cell*> s1 = {c1};
+  vector<cell*> s2 = {c2};
+  int best = 99999999;
+  int d0 = 0;
+
+  auto go_nearer = [&] (vector<cell*>& v, int& d) {
+    vector<cell*> w;
+    for(cell *c: v) 
+      forCellEx(c1, c) 
+        if(celldist(c1) < d)
+          w.push_back(c1);
+    sort(w.begin(), w.end());
+    d--; d0++;
+    auto last = std::unique(w.begin(), w.end());
+    w.erase(last, w.end());
+    v = w;
+    };
+
+  while(d0 < best) {  
+    for(cell *a1: s1) for(cell *a2: s2) {
+      if(a1 == a2) best = min(best, d0);
+      else if(isNeighbor(a1, a2)) best = min(best, d0+1);
+      }
+
+    if(d1 == 0 && d2 == 0) break;
+
+    if(d1 >= d2) go_nearer(s1, d1);
+    if(d1 < d2) go_nearer(s2, d2);
+    }
+  
+  return best;  
+  }
+
+
 EX int celldistance(cell *c1, cell *c2) {
   if(c1 == c2) return 0;
   if(c1 == currentmap->gamestart()) return c2->master->distance;
   if(c2 == currentmap->gamestart()) return c1->master->distance;
+  
+  if(geometry == gSpace534) return celldistance_534(c1, c2);
 
   auto r = regmap();