A few assorted cleanups.

luprex/core/cpp/world-core.cpp

@@ -403,10 +403,14 @@ void World::invoke_plan(int64_t actor_id, int64_t place_id, const std::string &a
 
     // Create a new thread, set up function and parameters.
     lua_State *CO = LS.newthread(thread);
+    
+    // Push the function to be invoked and its arguments.
     lua_pushvalue(L, func.index());
     lua_pushvalue(L, actor.index());
     lua_pushvalue(L, place.index());
     lua_pushvalue(L, invdata.index());
+
+    // Move actor, place, function and args to new thread.
     lua_xmove(L, CO, 4);
 
     // Store the thread into place's thread table.
@@ -454,7 +458,7 @@ void World::run_scheduled_threads(int64_t clk) {
         // Resume the coroutine.
         lua_State *CO = LS.ckthread(thread);
         int top = lua_gettop(CO);
-        int status = lua_resume(CO, nullptr, (top > 0) ? (top - 1) : 0);
+        int status = lua_resume(CO, nullptr, (top >= 4) ? 3 : 0);
 
         // Three possible outcomes: finished, yielded, or errored.
         if (status == LUA_YIELD) {