* src/tgba/tgbatba.hh, src/tgba/tgbatba.cc

(tgba_tba_proxy::state_is_accepting): New method.
* src/tgbaalgos/magic.hh, src/tgbaalgos/magic.cc: New files.
* src/tgbaalgos/Makefile.am (libtgbaalgos_la_SOURCES,
tgbaalgos_HEADERS): Add them.
* src/tgbatest/ltlmagic.cc, src/tgbatest/ltlmagic.test: New files.
* src/tgbatest/Makefile.am (TESTS, ltlmagic_SOURCES,
check_PROGRAMS): Add them.

src/tgbaalgos/magic.hh

@@ -0,0 +1,98 @@
+#ifndef SPOT_TGBAALGOS_MAGIC_HH
+# define SPOT_TGBAALGOS_MAGIC_HH
+
+#include <list>
+#include <utility>
+#include <ostream>
+#include "tgba/tgbatba.hh"
+
+namespace spot
+{
+  /// \brief Emptiness check on spot::tgba_tba_proxy automata using
+  /// the Magic Search algorithm. 
+  ///
+  /// This algorithm comes from
+  /// \verbatim
+  /// @InProceedings{   godefroid.93.pstv,
+  ///   author        = {Patrice Godefroid and Gerard .J. Holzmann},
+  ///   title         = {On the verification of temporal properties},
+  ///   booktitle     = {Proceedings of the 13th IFIP TC6/WG6.1 International
+  ///                   Symposium on Protocol Specification, Testing, and
+  ///                   Verification (PSTV'93)},
+  ///   month         = {May},
+  ///   editor        = {Andr{\'e} A. S. Danthine and Guy Leduc
+  ///                    and Pierre Wolper},
+  ///   address       = {Liege, Belgium},
+  ///   pages         = {109--124},
+  ///   publisher     = {North-Holland},
+  ///   year          = {1993},
+  ///   series        = {IFIP Transactions},
+  ///   volume        = {C-16},
+  ///   isbn          = {0-444-81648-8}
+  /// }
+  /// \endverbatim
+  struct magic_search
+  {
+    /// Initialize the Magic Search algorithm on the automaton \a a.
+    magic_search(const tgba_tba_proxy *a);
+    ~magic_search();
+
+    /// \brief Perform a Magic Search.
+    /// 
+    /// \return true iff the algorithm has found a new accepting
+    ///    path.
+    ///
+    /// check() can be called several times until it return false,
+    /// to enumerate all accepting paths.
+    bool check();
+
+    /// Print the last accepting path found.
+    std::ostream& print_result(std::ostream& os) const;
+
+  private:
+
+    // The names "stack", "h", and "x", are those used in the paper.
+
+    /// \brief  Records whether a state has be seen with the magic bit
+    /// on or off.
+    struct magic
+    {
+      bool seen_without : 1;
+      bool seen_with    : 1;
+    };
+    
+    /// \brief A state for the spot::magic_search algorithm.
+    struct magic_state
+    {
+      const state* s;
+      bool m;			///< The state of the magic demon.
+    };
+
+    typedef std::pair<magic_state, tgba_succ_iterator*> state_iter_pair;
+    typedef std::list<state_iter_pair> stack_type;
+    stack_type stack;		///< Stack of visited states on the path.
+
+    typedef std::list<bdd> tstack_type;
+    /// \brief Stack of transitions.  
+    ///
+    /// This is an addition to the data from the paper.
+    tstack_type tstack;
+
+    // FIXME: use a hash_map.
+    typedef std::map<const state*, magic, state_ptr_less_than> hash_type;
+    hash_type h;		///< Map of visited states.
+
+    /// Append a new state to the current path.
+    void push(const state* s, bool m);
+    /// Check whether we already visited \a s with the Magic bit set to \a m.
+    bool has(const state* s, bool m) const;
+
+    const tgba_tba_proxy* a;	///< The automata to check.
+    /// The state for which we are currently seeking an SCC.
+    const state* x;		
+  };
+
+
+}
+
+#endif // SPOT_TGBAALGOS_MAGIC_HH