twaalgos/cobuchi: Add nsa_to_nca()

* NEWS: Update.
* spot/twaalgos/cobuchi.hh: Declare to_dca() and nsa_to_nca().
* spot/twaalgos/cobuchi.cc: Implement them.
* python/spot/impl.i: Include new file for python bindings.
* spot/twaalgos/Makefile.am: Add new file.
* bin/autfilt.cc: Add --dca command line option. This option does not
return a deterministic automaton yet, but it will.
* tests/core/dca.test: Add tests for Büchi automata.
* tests/python/dca.py: Add a python script that builds a nondet. Streett
automaton.
* tests/python/dca.test: Add tests for Streett automata.
* tests/Makefile.am: Add all tests.

spot/twaalgos/cobuchi.hh

@@ -0,0 +1,91 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2017 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/>.
+
+#pragma once
+
+#include <spot/misc/bitvect.hh>
+#include <spot/twa/fwd.hh>
+
+#include <vector>
+
+namespace spot
+{
+  /// A vector of nca_st_info is given as argument to nsa_to_nca(). Each
+  /// nca_st_info has information about a state that must be seen infinitely
+  /// often. For a state 's' visited infinitely often by a run, the information
+  /// provided is:
+  ///  - the clause number satisfied by the run (from left to right)
+  ///  - the state number of 's'
+  ///  - destinations of all outgoing edges of 's' (represented as a bitvect)
+  struct nca_st_info
+  {
+    unsigned clause_num;
+    unsigned state_num;
+    bitvect* all_dst;
+
+    nca_st_info(unsigned clause, unsigned st, bitvect* dst)
+    {
+      clause_num = clause;
+      state_num = st;
+      all_dst = dst;
+    }
+
+    ~nca_st_info()
+    {
+      delete all_dst;
+    }
+  };
+
+  typedef std::vector<struct nca_st_info*> vect_nca_info;
+
+  /// \brief Converts a nondet Streett-like aut. to a nondet. co-Büchi aut.
+  ///
+  /// This function works in top of the augmented subset construction algorithm
+  /// and is described in section 3.1 of:
+  /** \verbatim
+      @Article{boker.2009.lcs,
+        author    = {Udi Boker and Orna Kupferman},
+        title     = {Co-Büching Them All},
+        booktitle = {Foundations of Software Science and Computational
+                     Structures - 14th International Conference, FOSSACS 2011}
+        year      = {2011},
+        pages     = {184--198},
+        url       = {\url{www.cs.huji.ac.il/~ornak/publications/fossacs11b.pdf}}
+      }
+      \endverbatim */
+  /// This implementation is quite different from the described algorithm. It
+  /// is made to work with automaton with Street-like acceptance (including
+  /// Büchi).
+  ///
+  /// \a aut The automaton to convert.
+  /// \a named_states name each state for easier debugging.
+  /// \a nca_info retrieve information about state visited infinitely often.
+  SPOT_API twa_graph_ptr
+  nsa_to_nca(const const_twa_graph_ptr& aut,
+             bool named_states = false,
+             vect_nca_info* nca_info = nullptr);
+
+  /// \brief Converts any ω-automata to det. co-buchi (when possible)
+  ///
+  /// The resulting automaton will always recognize at least the same language.
+  /// Actually, it can recognize more if the original language can not be
+  /// expressed using a co-Büchi acceptance condition.
+  SPOT_API twa_graph_ptr
+  to_dca(const const_twa_graph_ptr& aut, bool named_states = false);
+}