Simulation keeps track of simulated states in the input automaton.

* NEWS: Document the change.
* spot/twaalgos/simulation.cc: Implement the change.
* spot/twa/twagraph.cc: `copy_state_names_from` uses simulated states
  info if present.
* spot/twaalgos/determinize.cc: Pretty-print in determinization follows
  simulated states, avoiding possible confusion.
* tests/Makefile.am, tests/python/simstate.py: Add a test.

spot/twa/twagraph.cc

@@ -635,11 +635,22 @@ namespace spot
   {
     if (other == shared_from_this())
       return;
+
     auto orig = get_named_prop<std::vector<unsigned>>("original-states");
+    auto sims = get_named_prop<std::vector<unsigned>>("simulated-states");
+
+    if (orig && sims)
+      throw std::runtime_error("copy_state_names_from(): original-states and "
+                               "simulated-states are both set");
+
     if (orig && orig->size() != num_states())
       throw std::runtime_error("copy_state_names_from(): unexpected size "
                                "for original-states");
 
+    if (sims && sims->size() != other->num_states())
+      throw std::runtime_error("copy_state_names_from(): unexpected size "
+                               "for simulated-states");
+
     auto names = std::unique_ptr<std::vector<std::string>>
       (new std::vector<std::string>);
     unsigned ns = num_states();
@@ -647,11 +658,27 @@ namespace spot
 
     for (unsigned s = 0; s < ns; ++s)
       {
-        unsigned other_s = orig ? (*orig)[s] : s;
-        if (other_s >= ons)
-          throw std::runtime_error("copy_state_names_from(): state does not"
-                                   " exist in source automaton");
-        names->emplace_back(other->format_state(other_s));
+        std::string newname = "";
+        if (sims)
+          {
+            for (unsigned t = 0; t < ons; ++t)
+              {
+                if (s == (*sims)[t])
+                  newname += other->format_state(t) + ',';
+              }
+            assert(!newname.empty());
+            newname.pop_back(); // remove trailing comma
+            newname = '[' + newname + ']';
+          }
+        else
+          {
+            unsigned other_s = orig ? (*orig)[s] : s;
+            if (other_s >= ons)
+              throw std::runtime_error("copy_state_names_from(): state does not"
+                                       " exist in source automaton");
+            newname = other->format_state(other_s);
+          }
+        names->emplace_back(newname);
       }
 
     set_named_prop("state-names", names.release());

spot/twaalgos/determinize.cc

@@ -185,7 +185,8 @@ namespace spot
     }
 
     std::string
-    nodes_to_string(const safra_state::nodes_t& states)
+    nodes_to_string(const const_twa_graph_ptr& aut,
+                    const safra_state::nodes_t& states)
     {
       auto copy = sorted_nodes(states);
       std::ostringstream os;
@@ -223,7 +224,7 @@ namespace spot
             }
           if (!first)
             os << ' ';
-          os << n.first;
+          os << aut->format_state(n.first);
           first = false;
         }
       // Finish unwinding stack to print last braces
@@ -236,11 +237,12 @@ namespace spot
     }
 
     std::vector<std::string>*
-    print_debug(std::map<safra_state, int>& states)
+    print_debug(const const_twa_graph_ptr& aut,
+                const std::map<safra_state, int>& states)
     {
       auto res = new std::vector<std::string>(states.size());
-      for (auto& p: states)
-        (*res)[p.second] = nodes_to_string(p.first.nodes_);
+      for (const auto& p: states)
+        (*res)[p.second] = nodes_to_string(aut, p.first.nodes_);
       return res;
     }
 
@@ -576,11 +578,16 @@ namespace spot
 
     // Degeneralize
     twa_graph_ptr aut = spot::degeneralize_tba(a);
+    if (pretty_print)
+      aut->copy_state_names_from(a);
     std::vector<bdd> implications;
     if (use_simulation)
       {
         aut = spot::scc_filter(aut);
-        aut = simulation(aut, &implications);
+        auto aut2 = simulation(aut, &implications);
+        if (pretty_print)
+          aut2->copy_state_names_from(aut);
+        aut = aut2;
       }
     scc_info scc = scc_info(aut);
     std::vector<bool> is_connected = find_scc_paths(scc);
@@ -694,7 +701,7 @@ namespace spot
     res->prop_state_acc(false);
 
     if (pretty_print)
-      res->set_named_prop("state-names", print_debug(seen));
+      res->set_named_prop("state-names", print_debug(aut, seen));
     return res;
   }
 }

spot/twaalgos/simulation.cc

@@ -439,6 +439,10 @@ namespace spot
         res->copy_ap_of(a_);
         res->copy_acceptance_of(a_);
 
+        auto state_mapping = new std::vector<unsigned>();
+        state_mapping->resize(a_->num_states());
+        res->set_named_prop("simulated-states", state_mapping);
+
         // Non atomic propositions variables (= acc and class)
         bdd nonapvars = all_proms_ & bdd_support(all_class_var_);
 
@@ -454,6 +458,9 @@ namespace spot
             // its class, or by all the implied classes.
             auto s = gb->new_state(cl.id());
             gb->alias_state(s, relation_[cl].id());
+            // update state_mapping
+            for (auto& st : p.second)
+              (*state_mapping)[st] = s;
             if (implications)
               (*implications)[s] = relation_[cl];
           }