method for isolating world objects

src/types.cpp

@@ -283,6 +283,19 @@ PlanState::PlanState() {}
 PlanState::PlanState(const std::set<Predicate>& predicates) :
   predicates_(predicates) {}
 
+std::set<TermWrapper> PlanState::symbols() const
+{
+  std::set<TermWrapper> sym;
+  for (const Predicate& pred : predicates_)
+  {
+    for (const TermWrapper& arg : pred.get_arguments())
+    {
+      if (arg.get_literal_term()) sym.insert(arg);
+    }
+  }
+  return sym;
+}
+
 std::string PlanState::to_str() const
 {
   std::ostringstream oss;

src/types.h

@@ -318,6 +318,8 @@ class PlanState : public Stringifiable,
 
     PlanState(const std::set<Predicate>& predicates);
 
+    std::set<TermWrapper> symbols() const;
+
     virtual std::string to_str() const override;
 
     virtual std::size_t hash() const override;