Add a is_weak_scc() function based on cycle enumeration.

* src/tgbaalgos/isweakscc.cc, src/tgbaalgos/isweakscc.hh: New files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbatest/ltl2tgba.cc: Add a -KW option.
* src/tgbatest/cycles.test: Test it on a small example.

src/tgbaalgos/isweakscc.hh

@@ -0,0 +1,47 @@
+// Copyright (C) 2012 Laboratoire de Recherche et Developpement 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_ISWEAKSCC_HH
+# define SPOT_TGBAALGOS_ISWEAKSCC_HH
+
+#include "scc.hh"
+
+namespace spot
+{
+  /// \addtogroup tgba_misc
+  /// @{
+
+  /// \brief Whether the SCC number \a scc in \a aut is weak.
+  ///
+  /// An SCC is weak if its cycles are all accepting, or the are all
+  /// non-accepting.
+  ///
+  /// The scc_map \a map should have been built already.  The absence
+  /// of accepting cycle is easy to check (the scc_map can tell
+  /// whether the SCC is non-accepting already).  For the accepting
+  /// SCC, this function works by enumerating all cycles in the given
+  /// SCC (it stops if it find a non-accepting cycle).
+  bool is_weak_scc(const tgba* aut, scc_map& map, unsigned scc);
+
+  /// @}
+}
+
+
+#endif // SPOT_TGBAALGOS_ISWEAKSCC_HH