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/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