Introduce some masked tgba.

* src/tgba/tgbamask.cc, src/tgba/tgbamask.hh,
src/tgba/tgbaproxy.cc, src/tgba/tgbaproxy.hh: New files.
* src/tgba/Makefile.am: Add them.
* src/tgbatest/explicit3.cc, src/tgbatest/explicit3.test:
New files.
* src/tgbatest/Makefile.am: Add them.

src/tgba/tgbamask.hh

@@ -0,0 +1,85 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2013 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 3 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef SPOT_TGBA_TGBAMASK_HH
+# define SPOT_TGBA_TGBAMASK_HH
+
+#include "tgbaproxy.hh"
+
+namespace spot
+{
+
+  /// \ingroup tgba_on_the_fly_algorithms
+  /// \brief A masked TGBA (abstract).
+  ///
+  /// Ignores some states from a TGBA.  What state are preserved or
+  /// ignored is controlled by the wanted() method.
+  ///
+  /// This is an abstract class. You should inherit from it and
+  /// supply a wanted() method to specify which states to keep.
+  class SPOT_API tgba_mask: public tgba_proxy
+  {
+  protected:
+    /// \brief Constructor.
+    /// \param masked The automaton to mask
+    /// \param init Any state to use as initial state. This state will be
+    /// destroyed by the destructor.
+    tgba_mask(const tgba* masked, const state* init = 0);
+
+  public:
+    virtual ~tgba_mask();
+
+    virtual state* get_init_state() const;
+
+    virtual tgba_succ_iterator*
+    succ_iter(const state* local_state,
+	      const state* global_state = 0,
+	      const tgba* global_automaton = 0) const;
+
+    virtual bool wanted(const state* s) const = 0;
+
+  protected:
+    const state* init_;
+  };
+
+  /// \ingroup tgba_on_the_fly_algorithms
+  /// \brief Mask a TGBA, keeping a given set of states.
+  ///
+  /// Mask the TGBA \a to_mask, keeping only the
+  /// states from \a to_keep.  The initial state
+  /// can optionally be reset to \a init.
+  SPOT_API const tgba*
+  build_tgba_mask_keep(const tgba* to_mask,
+		       const state_set& to_keep,
+		       const state* init = 0);
+
+  /// \ingroup tgba_on_the_fly_algorithms
+  /// \brief Mask a TGBA, rejecting a given set of states.
+  ///
+  /// Mask the TGBA \a to_mask, keeping only the states that are not
+  /// in \a to_ignore.  The initial state can optionally be reset to
+  /// \a init.
+  SPOT_API const tgba*
+  build_tgba_mask_ignore(const tgba* to_mask,
+			 const state_set& to_ignore,
+			 const state* init = 0);
+
+}
+
+#endif // SPOT_TGBA_TGBAMASK_HH