Implement is_safety_automaton().

* src/tgbaalgos/safety.hh, src/tgbaalgos/safety.cc: New
files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbatests/ltl2tgba.cc: Add option "-O".
* src/tgbaalgos/scc.hh: Update documentation.
* src/tgbatest/Makefile.am (TESTS): Add safety.test.
* src/tgbatest/safety.test: New file.

src/tgbaalgos/Makefile.am

@@ -1,7 +1,8 @@
-## Copyright (C) 2003, 2004, 2005, 2008, 2009 Laboratoire
-## d'Informatique de Paris 6 (LIP6),
-## département Systèmes Répartis Coopératifs (SRC), Université Pierre
-## et Marie Curie.
+## Copyright (C) 2008, 2009, 2010 Laboratoire de Recherche et
+## Développement de l'Epita (LRDE).
+## Copyright (C) 2003, 2004, 2005 Laboratoire d'Informatique de Paris
+## 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
+## Université Pierre et Marie Curie.
 ##
 ## This file is part of Spot, a model checking library.
 ##
@@ -51,6 +52,7 @@ tgbaalgos_HEADERS = \
   reducerun.hh \
   replayrun.hh \
   rundotdec.hh \
+  safety.hh \
   save.hh \
   scc.hh \
   sccfilter.hh \
@@ -86,6 +88,7 @@ libtgbaalgos_la_SOURCES = \
   reducerun.cc \
   replayrun.cc \
   rundotdec.cc \
+  safety.cc \
   save.cc \
   scc.cc \
   sccfilter.cc \

src/tgbaalgos/safety.cc

@@ -0,0 +1,75 @@
+// Copyright (C) 2010 Laboratoire de Recherche et Développement de
+// l'Epita (LRDE)
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Spot; see the file COPYING.  If not, write to the Free
+// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+
+#include "safety.hh"
+
+namespace spot
+{
+  bool
+  is_safety_automaton(const tgba* aut, const scc_map* sm)
+  {
+    // Create an scc_map of the user did not give one to us.
+    bool need_sm = !sm;
+    if (need_sm)
+      {
+	scc_map* x = new scc_map(aut);
+	x->build_map();
+	sm = x;
+      }
+
+    bool result = true;
+
+    unsigned scc_count = sm->scc_count();
+    for (unsigned scc = 0; (scc < scc_count) && result; ++scc)
+      {
+	if (!sm->accepting(scc))
+	  continue;
+	// Accepting SCCs should have only one state.
+	const std::list<const state*>& st = sm->states_of(scc);
+	if (st.size() != 1)
+	  {
+	    result = false;
+	    break;
+	  }
+	// The state should have only one transition that is a
+	// self-loop labelled by true.
+	const state* s = *st.begin();
+	tgba_succ_iterator* it = aut->succ_iter(s);
+	it->first();
+	assert(!it->done());
+	state* dest = it->current_state();
+	bdd cond = it->current_condition();
+	it->next();
+	result = (!dest->compare(s)) && it->done() && (cond == bddtrue);
+	delete dest;
+	delete it;
+      }
+
+    // Free the scc_map if we created it.
+    if (need_sm)
+      delete sm;
+
+    return result;
+  }
+
+
+
+
+}

src/tgbaalgos/safety.hh

@@ -0,0 +1,44 @@
+// Copyright (C) 2010 Laboratoire de Recherche et Développement de
+// l'Epita (LRDE)
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Spot; see the file COPYING.  If not, write to the Free
+// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+
+#ifndef SPOT_TGBAALGOS_SAFETY_HH
+# define SPOT_TGBAALGOS_SAFETY_HH
+
+#include "scc.hh"
+
+namespace spot
+{
+  /// \brief Whether an automaton is a safety property.
+  ///
+  /// An automaton is an safety if any accepting path ends on an
+  /// accepting state with only one transition that is a self-loop
+  /// labelled by true.  Note that this is only a sufficient
+  /// condition.  Some safety automata might not be recognized with
+  /// this check because of some non-determinism in the automaton.
+  ///
+  /// \param aut the automaton to check
+  ///
+  /// \param sm an scc_map of the automaton if available (it will be
+  /// built otherwise.  If you supply an scc_map you should call
+  /// build_map() before passing it to this function.
+  bool is_safety_automaton(const tgba* aut, const scc_map* sm = 0);
+}
+
+#endif // SPOT_TGBAALGOS_SAFETY_HH

src/tgbaalgos/scc.hh

@@ -1,5 +1,5 @@
-// Copyright (C) 2008, 2009  Laboratoire de Recherche et Developpement de
-// l'Epita.
+// Copyright (C) 2008, 2009, 2010 Laboratoire de Recherche et
+// Developpement de l'Epita.
 //
 // This file is part of Spot, a model checking library.
 //
@@ -90,6 +90,8 @@ namespace spot
 
     /// \brief Get the number of SCC in the automaton.
     ///
+    /// SCCs are labelled from 0 to scc_count()-1.
+    ///
     /// \pre This should only be called once build_map() has run.
     unsigned scc_count() const;