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/Makefile.am

@@ -42,6 +42,7 @@ tgbaalgos_HEADERS = \
   emptiness_stats.hh \
   gv04.hh \
   isdet.hh \
+  isweakscc.hh \
   lbtt.hh \
   ltl2taa.hh \
   ltl2tgba_fm.hh \
@@ -82,6 +83,7 @@ libtgbaalgos_la_SOURCES = \
   emptiness.cc \
   gv04.cc \
   isdet.cc \
+  isweakscc.cc \
   lbtt.cc \
   ltl2taa.cc \
   ltl2tgba_fm.cc \

src/tgbaalgos/isweakscc.cc

@@ -0,0 +1,83 @@
+// 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_CC
+# define SPOT_TGBAALGOS_ISWEAKSCC_CC
+
+#include "cycles.hh"
+
+namespace spot
+{
+  namespace
+  {
+    class weak_checker: public enumerate_cycles
+    {
+    public:
+      bool result;
+
+      weak_checker(const tgba* aut, const scc_map& map)
+	: enumerate_cycles(aut, map), result(true)
+      {
+      }
+
+      virtual bool
+      cycle_found(const state* start)
+      {
+	dfs_stack::const_iterator i = dfs.begin();
+	bdd acc = bddfalse;
+	while (i->ts->first != start)
+	  ++i;
+	do
+	  {
+	    acc |= i->succ->current_acceptance_conditions();
+	    ++i;
+	  }
+	while (i != dfs.end());
+	if (acc != aut_->all_acceptance_conditions())
+	  {
+	    // We have found an non-accepting cycle, so the SCC is not
+	    // weak.
+	    result = false;
+	    return false;
+	  }
+	return true;
+      }
+
+    };
+
+  }
+
+  bool
+  is_weak_scc(const tgba* aut, scc_map& map, unsigned scc)
+  {
+    // If no cycle is accepting, the SCC is weak.
+    if (!map.accepting(scc))
+      return true;
+    // If the SCC is accepting, but one cycle is not, the SCC is not
+    // weak.
+    weak_checker w(aut, map);
+    w.run(scc);
+    return w.result;
+  }
+
+
+}
+
+#endif // SPOT_TGBAALGOS_ISWEAKSCC_CC

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