dot: add a <N option

* spot/twaalgos/dot.cc: Implement it.
* spot/taalgos/dot.cc: Ignore it.
* spot/twaalgos/copy.cc, spot/twaalgos/copy.hh: Add option
to limit the number of states.
* tests/python/ltsmin.ipynb: Improve test case.
* tests/Makefile.am: Cleanup the files generated by ltsmin.ipynb.
* python/spot/__init__.py (setup): Add a max_states argument
that default to 50.
* bin/common_aoutput.cc: Mention the <INT option.
* NEWS: Likewise.

spot/twaalgos/copy.cc

@@ -27,13 +27,15 @@
 namespace spot
 {
   twa_graph_ptr
-  copy(const const_twa_ptr& aut, twa::prop_set p, bool preserve_names)
+  copy(const const_twa_ptr& aut, twa::prop_set p,
+       bool preserve_names, unsigned max_states)
   {
     twa_graph_ptr out = make_twa_graph(aut->get_dict());
     out->copy_acceptance_of(aut);
     out->copy_ap_of(aut);
     out->prop_copy(aut, p);
     std::vector<std::string>* names = nullptr;
+    std::set<unsigned>* incomplete = nullptr;
     if (preserve_names)
       {
 	names = new std::vector<std::string>;
@@ -69,9 +71,27 @@ namespace spot
 	unsigned src2;
 	std::tie(src1, src2) = *todo.front();
 	todo.pop_front();
-
 	for (auto* t: aut->succ(src1))
-	  out->new_edge(src2, new_state(t->dst()), t->cond(), t->acc());
+	  {
+	    if (SPOT_UNLIKELY(max_states < out->num_states()))
+	      {
+		// If we have reached the max number of state, never try
+		// to create a new one.
+		auto i = seen.find(t->dst());
+		if (i == seen.end())
+		  {
+		    if (!incomplete)
+		      incomplete = new std::set<unsigned>;
+		    incomplete->insert(src2);
+		    continue;
+		  }
+		out->new_edge(src2, i->second, t->cond(), t->acc());
+	      }
+	    else
+	      {
+		out->new_edge(src2, new_state(t->dst()), t->cond(), t->acc());
+	      }
+	  }
       }
 
 
@@ -84,6 +104,8 @@ namespace spot
 	ptr->destroy();
       }
 
+    if (incomplete)
+      out->set_named_prop("incomplete-states", incomplete);
     return out;
   }
 }

spot/twaalgos/copy.hh

@@ -33,5 +33,6 @@ namespace spot
   ///
   /// This works for using the abstract interface for automata
   SPOT_API twa_graph_ptr
-  copy(const const_twa_ptr& aut, twa::prop_set p, bool preserve_names = false);
+  copy(const const_twa_ptr& aut, twa::prop_set p,
+       bool preserve_names = false, unsigned max_states = -1U);
 }

spot/twaalgos/dot.cc

@@ -57,6 +57,7 @@ namespace spot
       const_twa_graph_ptr aut_;
       std::vector<std::string>* sn_ = nullptr;
       std::vector<std::pair<unsigned, unsigned>>* sprod_ = nullptr;
+      std::set<unsigned>* incomplete_;
       std::string* name_ = nullptr;
       acc_cond::mark_t inf_sets_ = 0U;
       acc_cond::mark_t fin_sets_ = 0U;
@@ -83,9 +84,21 @@ namespace spot
 	};
       const char*const* palette = palette9;
       int palette_mod = 9;
+      unsigned max_states_ = -1U;
+      bool max_states_given_ = false;
 
     public:
 
+      unsigned max_states()
+      {
+	return max_states_;
+      }
+
+      bool max_states_given()
+      {
+	return max_states_given_;
+      }
+
       void
       parse_opts(const char* options)
       {
@@ -95,7 +108,7 @@ namespace spot
 	    {
 	    case '.':
 	      {
-	        // Copy the value in a string, so future calls to
+		// Copy the value in a string, so future calls to
 		// parse_opts do not fail if the environment has
 		// changed.  (This matters particularly in an ipython
 		// notebook, where it is tempting to redefine
@@ -123,6 +136,25 @@ namespace spot
 		options = end;
 		break;
 	      }
+	    case '<':
+	      {
+		char* end;
+		max_states_ = strtoul(options, &end, 10);
+		if (options == end)
+		  throw std::runtime_error
+		    ("missing number after '<' in print_dot() options");
+		if (max_states_ == 0)
+		  {
+		    max_states_ = -1U;
+		    max_states_given_ = false;
+		  }
+		else
+		  {
+		    max_states_given_ = true;
+		  }
+		options = end;
+		break;
+	      }
 	    case '1':
 	      opt_want_state_names_ = false;
 	      break;
@@ -445,6 +477,9 @@ namespace spot
 	      os_ << ", peripheries=2";
 	    os_ << "]\n";
 	  }
+	if (incomplete_ && incomplete_->find(s) != incomplete_->end())
+	  os_ << "  u" << s << " [label=\"...\", shape=none, width=0, height=0"
+	    "]\n  " << s << " -> u" << s << " [style=dashed]\n";
       }
 
       void
@@ -497,6 +532,8 @@ namespace spot
 		  sprod_ = nullptr;
 	      }
 	  }
+	incomplete_ =
+	  aut->get_named_prop<std::set<unsigned>>("incomplete-states");
 	if (opt_name_)
 	  name_ = aut_->get_named_prop<std::string>("automaton-name");
 	mark_states_ = (!opt_force_acc_trans_
@@ -566,8 +603,8 @@ namespace spot
   {
     dotty_output d(os, options);
     auto aut = std::dynamic_pointer_cast<const twa_graph>(g);
-    if (!aut)
-      aut = copy(g, twa::prop_set::all(), true);
+    if (!aut || (d.max_states_given() && aut->num_states() >= d.max_states()))
+      aut = copy(g, twa::prop_set::all(), true, d.max_states() - 1);
     d.print(aut);
     return os;
   }