diff --git a/luprex/cpp/core/world-pairtab.cpp b/luprex/cpp/core/world-pairtab.cpp
index 81004b60..e5210bda 100644
--- a/luprex/cpp/core/world-pairtab.cpp
+++ b/luprex/cpp/core/world-pairtab.cpp
@@ -20,47 +20,23 @@ int World::number_lua_tables(const IdVector &basis) {
     // This is conceptually recursive, but we're going to use an
     // explicit stack (the lua stack).
     lua_State *L = state();
-    LuaVar tnmap, ntmap, tangibles, tab, key, val, xid;
-    LuaOldStack LS(L, tnmap, ntmap, tangibles, tab, key, val, xid);
-    LS.set(tnmap, LuaNewTable);
-    LS.set(ntmap, LuaNewTable);
-    LS.rawset(LuaRegistry, "tnmap", tnmap);
-    LS.rawset(LuaRegistry, "ntmap", ntmap);
-    LS.rawget(tangibles, LuaRegistry, "tangibles");
     int nextid = 1;
-    int top = lua_gettop(L);
+    {
+        LuaVar tnmap, ntmap, tangibles, tab, key, val, xid;
+        LuaExtStack LS(L, tnmap, ntmap, tangibles, tab, key, val, xid);
+        LS.set(tnmap, LuaNewTable);
+        LS.set(ntmap, LuaNewTable);
+        LS.rawset(LuaRegistry, "tnmap", tnmap);
+        LS.rawset(LuaRegistry, "ntmap", ntmap);
+        LS.rawget(tangibles, LuaRegistry, "tangibles");
+        int top = lua_gettop(L);
 
-    // Push all subtables onto the stack.  Note that we may push
-    // the same table twice, that's OK.
-    for (int64_t id : basis) {
-        LS.rawget(tab, tangibles, id);
-        assert(LS.istable(tab));
-        // Traverse subtables.
-        LS.set(key, LuaNil);
-        while (LS.next(tab, key, val)) {
-            if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
-                lua_checkstack(L, 10);
-                lua_pushvalue(L, val.index());
-            }
-        }
-    }
-
-    // Pop tables from the stack one by one.  If the table is not
-    // already numbered, number it and push subtables onto the stack.
-    while (lua_gettop(L) > top) {
-        lua_replace(L, tab.index());
-        LS.rawget(xid, tnmap, tab);
-        if (LS.isnil(xid)) {
-            int id = nextid++;
-            LS.rawset(tnmap, tab, id);
-            LS.rawset(ntmap, id, tab);
-            // Traverse the metatable.
-            LS.getmetatable(val, tab);
-            if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
-                lua_checkstack(L, 10);
-                lua_pushvalue(L, val.index());
-            }
-            // Traverse the subtables.
+        // Push all subtables onto the stack.  Note that we may push
+        // the same table twice, that's OK.
+        for (int64_t id : basis) {
+            LS.rawget(tab, tangibles, id);
+            assert(LS.istable(tab));
+            // Traverse subtables.
             LS.set(key, LuaNil);
             while (LS.next(tab, key, val)) {
                 if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
@@ -69,9 +45,34 @@ int World::number_lua_tables(const IdVector &basis) {
                 }
             }
         }
+
+        // Pop tables from the stack one by one.  If the table is not
+        // already numbered, number it and push subtables onto the stack.
+        while (lua_gettop(L) > top) {
+            lua_replace(L, tab.index());
+            LS.rawget(xid, tnmap, tab);
+            if (LS.isnil(xid)) {
+                int id = nextid++;
+                LS.rawset(tnmap, tab, id);
+                LS.rawset(ntmap, id, tab);
+                // Traverse the metatable.
+                LS.getmetatable(val, tab);
+                if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
+                    lua_checkstack(L, 10);
+                    lua_pushvalue(L, val.index());
+                }
+                // Traverse the subtables.
+                LS.set(key, LuaNil);
+                while (LS.next(tab, key, val)) {
+                    if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
+                        lua_checkstack(L, 10);
+                        lua_pushvalue(L, val.index());
+                    }
+                }
+            }
+        }
     }
 
-    LS.result();
     assert(stack_is_clear());
     return nextid - 1;
 }
@@ -79,8 +80,8 @@ int World::number_lua_tables(const IdVector &basis) {
 void World::pair_lua_tables(const IdVector &basis, lua_State *master) {
     lua_State *synch = state();
     LuaVar stangibles, mtangibles, sntmap, mntmap, stnmap, mtnmap, stab, mtab, skey, mkey, sval, mval, sidx, midx;
-    LuaOldStack SLS(synch, stangibles, stab, skey, sval, sntmap, stnmap, sidx);
-    LuaOldStack MLS(master, mtangibles, mtab, mkey, mval, mntmap, mtnmap, midx);
+    LuaExtStack SLS(synch, stangibles, stab, skey, sval, sntmap, stnmap, sidx);
+    LuaExtStack MLS(master, mtangibles, mtab, mkey, mval, mntmap, mtnmap, midx);
 
     // Fetch the tangible databases
     SLS.rawget(stangibles, LuaRegistry, "tangibles");
@@ -168,63 +169,29 @@ void World::pair_lua_tables(const IdVector &basis, lua_State *master) {
             lua_pushvalue(synch, sval.index());
         }
     }
-
-    MLS.result();
-    SLS.result();
 }
 
 int World::number_remaining_tables(const IdVector &basis, lua_State *master) {
     // This is conceptually recursive, but we're going to use an
     // explicit stack (the lua stack).
-    lua_State *L = master;
-    LuaVar tnmap, ntmap, tangibles, tab, key, val, xid;
-    LuaOldStack LS(L, tnmap, ntmap, tangibles, tab, key, val, xid);
-    LS.rawget(tnmap, LuaRegistry, "tnmap");
-    LS.rawget(ntmap, LuaRegistry, "ntmap");
-    LS.rawget(tangibles, LuaRegistry, "tangibles");
-    int ntables = LS.rawlen(ntmap);
     eng::vector<bool> visited;
-    visited.assign(ntables + 1, false);
-    int top = lua_gettop(L);
+    int ntables;
+    {
+        lua_State *L = master;
+        LuaVar tnmap, ntmap, tangibles, tab, key, val, xid;
+        LuaExtStack LS(L, tnmap, ntmap, tangibles, tab, key, val, xid);
+        LS.rawget(tnmap, LuaRegistry, "tnmap");
+        LS.rawget(ntmap, LuaRegistry, "ntmap");
+        LS.rawget(tangibles, LuaRegistry, "tangibles");
+        ntables = LS.rawlen(ntmap);
+        visited.assign(ntables + 1, false);
+        int top = lua_gettop(L);
 
-    // Push all subtables onto the stack.  Note that we may push
-    // the same table twice, that's OK.
-    for (int64_t id : basis) {
-        LS.rawget(tab, tangibles, id);
-        assert(LS.istable(tab));
-        LS.set(key, LuaNil);
-        while (LS.next(tab, key, val)) {
-            if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
-                lua_checkstack(L, 10);
-                lua_pushvalue(L, val.index());
-            }
-        }
-    }
-
-    // Pop tables from the stack one by one.  If the table is not
-    // numbered, number it.  If it is not visited, visit it.
-    while (lua_gettop(L) > top) {
-        lua_replace(L, tab.index());
-        int id = 0;
-        LS.rawget(xid, tnmap, tab);
-        if (!LS.isnumber(xid)) {
-            id = visited.size();
-            LS.rawset(tnmap, tab, id);
-            LS.rawset(ntmap, id, tab);
-            visited.push_back(false);
-        } else {
-            id = LS.cknumber(xid);
-            assert((id >= 0) && (id < int(visited.size())));
-        }
-        if (!visited[id]) {
-            visited[id] = true;
-            // Traverse the metatable.
-            LS.getmetatable(val, tab);
-            if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
-                lua_checkstack(L, 10);
-                lua_pushvalue(L, val.index());
-            }
-            // Traverse the subtables.
+        // Push all subtables onto the stack.  Note that we may push
+        // the same table twice, that's OK.
+        for (int64_t id : basis) {
+            LS.rawget(tab, tangibles, id);
+            assert(LS.istable(tab));
             LS.set(key, LuaNil);
             while (LS.next(tab, key, val)) {
                 if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
@@ -233,35 +200,68 @@ int World::number_remaining_tables(const IdVector &basis, lua_State *master) {
                 }
             }
         }
-    }
 
-    LS.result();
+        // Pop tables from the stack one by one.  If the table is not
+        // numbered, number it.  If it is not visited, visit it.
+        while (lua_gettop(L) > top) {
+            lua_replace(L, tab.index());
+            int id = 0;
+            LS.rawget(xid, tnmap, tab);
+            if (!LS.isnumber(xid)) {
+                id = visited.size();
+                LS.rawset(tnmap, tab, id);
+                LS.rawset(ntmap, id, tab);
+                visited.push_back(false);
+            } else {
+                id = LS.cknumber(xid);
+                assert((id >= 0) && (id < int(visited.size())));
+            }
+            if (!visited[id]) {
+                visited[id] = true;
+                // Traverse the metatable.
+                LS.getmetatable(val, tab);
+                if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
+                    lua_checkstack(L, 10);
+                    lua_pushvalue(L, val.index());
+                }
+                // Traverse the subtables.
+                LS.set(key, LuaNil);
+                while (LS.next(tab, key, val)) {
+                    if (LS.istable(val) && LS.gettabletype(val)==LUA_TT_GENERAL) {
+                        lua_checkstack(L, 10);
+                        lua_pushvalue(L, val.index());
+                    }
+                }
+            }
+        }
+    }
     assert(stack_is_clear());
     return visited.size() - 1 - ntables;
 }
 
 void World::create_new_tables(int n) {
-    LuaVar tnmap, ntmap, tab;
-    LuaOldStack LS(state(), tnmap, ntmap, tab);
-    LS.rawget(tnmap, LuaRegistry, "tnmap");
-    LS.rawget(ntmap, LuaRegistry, "ntmap");
-    assert(LS.istable(tnmap));
-    assert(LS.istable(ntmap));
-    int ntables = LS.rawlen(ntmap);
-    int nextid = ntables + 1;
-    for (int i = 0; i < n; i++) {
-        int id = nextid++;
-        LS.newtable(tab);
-        LS.rawset(ntmap, id, tab);
-        LS.rawset(tnmap, tab, id);
+    {
+        LuaVar tnmap, ntmap, tab;
+        LuaExtStack LS(state(), tnmap, ntmap, tab);
+        LS.rawget(tnmap, LuaRegistry, "tnmap");
+        LS.rawget(ntmap, LuaRegistry, "ntmap");
+        assert(LS.istable(tnmap));
+        assert(LS.istable(ntmap));
+        int ntables = LS.rawlen(ntmap);
+        int nextid = ntables + 1;
+        for (int i = 0; i < n; i++) {
+            int id = nextid++;
+            LS.newtable(tab);
+            LS.rawset(ntmap, id, tab);
+            LS.rawset(tnmap, tab, id);
+        }
     }
-    LS.result();
     assert(stack_is_clear());
 }
 
 void World::unnumber_lua_tables() {
     // All we have to do is remove these tables from the registry.
-    LuaOldStack LS(state());
+    LuaExtStack LS(state());
     LS.rawset(LuaRegistry, "tnmap", LuaNil);
     LS.rawset(LuaRegistry, "ntmap", LuaNil);
 }