* src/misc/modgray.hh, src/misc/modgray.cc: New files.

* src/misc/Makefile.am (libmisc_la_SOURCES, misc_HEADERS): Add them.
* wrap/python/spot.i: Activate directors, and interface modgray.hh.
* wrap/python/tests/modgray.py: New file.
* wrap/python/tests/Makefile.am (TESTS): Add it.

ChangeLog

+2004-10-20  Alexandre Duret-Lutz  <adl@src.lip6.fr>
+
+	* src/misc/modgray.hh, src/misc/modgray.cc: New files.
+	* src/misc/Makefile.am (libmisc_la_SOURCES, misc_HEADERS): Add them.
+	* wrap/python/spot.i: Activate directors, and interface modgray.hh.
+	* wrap/python/tests/modgray.py: New file.
+	* wrap/python/tests/Makefile.am (TESTS): Add it.
+
 2004-10-18  Alexandre Duret-Lutz  <adl@src.lip6.fr>
 
 	* iface/gspn/gspn.cc, src/ltlvisit/basicreduce.cc,

src/misc/Makefile.am

@@ -31,6 +31,7 @@ misc_HEADERS = \
   freelist.hh \
   hash.hh \
   minato.hh \
+  modgray.hh \
   version.hh
 
 noinst_LTLIBRARIES = libmisc.la
@@ -39,4 +40,5 @@ libmisc_la_SOURCES = \
   escape.cc \
   freelist.cc \
   minato.cc \
+  modgray.cc \
   version.cc

src/misc/modgray.cc

+// Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
+// dpartement Systmes Rpartis Coopratifs (SRC), Universit Pierre
+// et Marie Curie.
+//
+// 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.
+
+#include "modgray.hh"
+
+namespace spot
+{
+
+  loopless_modular_mixed_radix_gray_code::
+  loopless_modular_mixed_radix_gray_code(int n)
+    : n_(n), a_(0), f_(0), m_(0), s_(0), non_one_radixes_(0)
+  {
+  }
+
+  loopless_modular_mixed_radix_gray_code::
+  ~loopless_modular_mixed_radix_gray_code()
+  {
+    delete[] a_;
+    delete[] f_;
+    delete[] m_;
+    delete[] s_;
+    delete[] non_one_radixes_;
+  }
+
+  void
+  loopless_modular_mixed_radix_gray_code::first()
+  {
+    if (!non_one_radixes_)
+      {
+	// This computation needs to be done only once, but we cannot
+	// do it in the constructor because it involves virtual
+	// functions.
+
+	// non_one_radixes_ needs to hold at most n_ integer, maybe less
+	// we do not know yet and do not care (saving these extra bytes
+	// would require two loops over a_last(j); this doesn't seem
+	// worth the hassle).  We update n_ before allocating the other
+	// arrays.
+	non_one_radixes_ = new int[n_];
+	int k = 0;
+	for (int j = 0; j < n_; ++j)
+	  {
+	    a_first(j);
+	    if (!a_last(j))
+	      non_one_radixes_[k++] = j;
+	  }
+	n_ = k;
+	a_ = new int[k];
+	f_ = new int[k + 1];
+	m_ = new int[k];
+	s_ = new int[k];
+
+	for (int j = 0; j < n_; ++j)
+	  m_[j] = -1;
+	f_[n_] = n_;
+      }
+
+    // Reset everything except m_[j] (let's preserve discovered
+    // radixes between runs) and f_[n_] (never changes).
+    for (int j = 0; j < n_; ++j)
+      {
+	a_[j] = 0;
+	a_first(non_one_radixes_[j]);
+	s_[j] = m_[j];
+	f_[j] = j;
+      }
+    done_ = false;
+  }
+
+  // Update one item of the tuple and return its position.
+  int
+  loopless_modular_mixed_radix_gray_code::next()
+  {
+    int j = f_[0];
+
+    if (j == n_)
+      {
+	done_ = true;
+	return -1;
+      }
+
+    f_[0] = 0;
+
+    int real_j = non_one_radixes_[j];
+
+    if (a_[j] == m_[j])
+      {
+	a_[j] = 0;
+	a_first(real_j);
+      }
+    else
+      {
+	++a_[j];
+	a_next(real_j);
+	// Discover the radix on-the-fly.
+	if (m_[j] == -1 && a_last(real_j))
+	  s_[j] = m_[j] = a_[j];
+      }
+
+    if (a_[j] == s_[j])
+      {
+	--s_[j];
+	if (s_[j] < 0)
+	  s_[j] = m_[j];
+	f_[j] = f_[j + 1];
+	f_[j + 1] = j + 1;
+      }
+
+    return real_j;
+  }
+
+} // spot

src/misc/modgray.hh

+// Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
+// département Systèmes Répartis Coopératifs (SRC), Université Pierre
+// et Marie Curie.
+//
+// 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_MISC_MODGRAY_HH
+# define SPOT_MISC_MODGRAY_HH
+
+namespace spot
+{
+
+  /// \brief Loopless modular mixed radix Gray code iteration.
+  ///
+  /// This class is based on the loopless modular mixed radix gray
+  /// code algorithm described in exercise 77 of "The Art of Computer
+  /// Programming", Pre-Fascicle 2A (Draft of section 7.2.1.1:
+  /// generating all n-tuples) by Donald E. Knuth.
+  ///
+  /// The idea is to enumerate the set of all n-tuples
+  /// (a<sub>0</sub>,a<sub>1</sub>,...,a<sub>n-1</sub>) where each
+  /// a<sub>j</sub> range over a distinct set (this is the <i>mixed
+  /// radix</i> part), so that only one a<sub>j</sub> changes between
+  /// two successive tuples of the iteration (that is the <i>Gray
+  /// code</i> part), and that this changes occurs always in the same
+  /// direction, cycling over the set a<sub>j</sub> must cover (i.e.,
+  /// <i>modular</i>).  The algorithm is <i>loopless</i> in that
+  /// computing the next tuple done without any loop, i.e., in
+  /// constant time.
+  ///
+  /// This class does not need to know the type of the a<sub>j</sub>,
+  /// it will handle them indirectly through three methods: a_first(),
+  /// a_next(), and a_last().  These methods need to be implemented
+  /// in a subclass for the particular type of a<sub>j</sub> at hand.
+  ///
+  /// The class itself offers four functions to control the iteration
+  /// over the set of all the (a<sub>0</sub>,a<sub>1</sub>,...,
+  /// a<sub>n-1</sub>) tuples: first(), next(), last(), and done().
+  /// These functions are usually used as follows:
+  /// \code
+  ///    for (g.first(); !g.done(); g.next())
+  ///       use the tuple
+  /// \endcode
+  /// How to use the tuple of course depends on the way
+  /// it as been stored in the subclass.
+  ///
+  /// Finally, let's mention two differences between this algorithm
+  /// and the one in Knuth's book.  This version of the algorithm does
+  /// not need to know the radixes (i.e., the size of set of each
+  /// a<sub>j</sub>) beforehand: it will discover them on-the-fly when
+  /// a_last(j) first return true.  It will also work with
+  /// a<sub>j</sub> that cannot be changed.  (This is achieved by
+  /// reindexing the elements through \c non_one_radixes_, to consider
+  /// only the elements with a non-singleton range.)
+  class loopless_modular_mixed_radix_gray_code
+  {
+  public:
+    /// Constructor.
+    ///
+    /// \param n The size of the tuples to enumerate.
+    loopless_modular_mixed_radix_gray_code(int n);
+
+    virtual ~loopless_modular_mixed_radix_gray_code();
+
+    /// \name iteration over an element in a tuple
+    ///
+    /// The class does not know how to modify the elements of the
+    /// tuple (Knuth's a<sub>j</sub>s).  These changes are therefore
+    /// abstracted using the a_first(), a_next(), and a_last()
+    /// abstract functions.  These need to be implemented in
+    /// subclasses as appropriate.
+    ///
+    /// @{
+
+    /// Reset a<sub>j</sub> to its initial value.
+    virtual void a_first(int j) = 0;
+    /// \brief Advance a<sub>j</sub> to its next value.
+    ///
+    /// This will never be called if a_last(j) is true.
+    virtual void a_next(int j) = 0;
+    /// Whether a<sub>j</sub> is on its last value.
+    virtual bool a_last(int j) const = 0;
+    /// @}
+
+    /// \name iteration over all the tuples
+    /// @{
+
+    /// \brief Reset the iteration to the first tuple.
+    ///
+    /// This must be called before calling any of next(), last(), or done().
+    void first();
+
+    /// \brief Whether this the last tuple.
+    ///
+    /// At this point it is still OK to call next(), and then done() will
+    /// become true.
+    bool
+    last()
+    {
+      return f_[0] == n_;
+    }
+
+    /// Whether all tuple have been explored.
+    bool
+    done()
+    {
+      return done_;
+    }
+
+    /// \brief Update one item of the tuple and return its position.
+    ///
+    /// next() should never be called if done() is true.  If it is
+    /// called on the last tuple (i.e., last() is true), it will return
+    /// -1.  Otherwise it will update one a<sub>j</sub> of the tuple
+    /// through one the a<sub>j</sub> handling functions, and return j.
+    int next();
+    /// @}
+
+  protected:
+    int n_;
+    bool done_;
+    int* a_;
+    int* f_;
+    int* m_;
+    int* s_;
+    int* non_one_radixes_;
+  };
+
+} // spot
+
+# endif // SPOT_MISC_MODGRAY_HH

wrap/python/spot.i

@@ -19,7 +19,7 @@
 // Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 // 02111-1307, USA.
 
-%module spot
+%module(directors="1") spot
 
 %include "std_string.i"
 %include "std_list.i"
@@ -35,6 +35,7 @@
 #include "misc/version.hh"
 #include "misc/bddalloc.hh"
 #include "misc/minato.hh"
+#include "misc/modgray.hh"
 
 #include "ltlast/formula.hh"
 #include "ltlast/refformula.hh"
@@ -91,6 +92,9 @@ using namespace spot;
 %include "misc/bddalloc.hh"
 %include "misc/minato.hh"
 
+%feature("director") spot::loopless_modular_mixed_radix_gray_code;
+%include "misc/modgray.hh"
+
 %include "ltlast/formula.hh"
 %include "ltlast/refformula.hh"
 %include "ltlast/atomic_prop.hh"

wrap/python/tests/Makefile.am

@@ -33,4 +33,5 @@ TESTS = \
   bddnqueen.py \
   ltl2tgba.test \
   interdep.py \
-  minato.py
+  minato.py \
+  modgray.py

wrap/python/tests/modgray.py

+# -*- mode: python; coding: iso-8859-1 -*-
+# Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
+# dpartement Systmes Rpartis Coopratifs (SRC), Universit Pierre
+# et Marie Curie.
+#
+# 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.
+
+import ltihooks
+import spot
+
+class test(spot.loopless_modular_mixed_radix_gray_code):
+    def __init__(self, lim):
+        spot.loopless_modular_mixed_radix_gray_code.__init__(self, len(lim))
+        self.msg = list(lim)
+        self.lim = list(lim)
+
+    def a_first(self, j):
+        self.msg[j] = 'a'
+
+    def a_next(self, j):
+        self.msg[j] = chr(1 + ord(self.msg[j]))
+
+    def a_last(self, j):
+        return self.msg[j] == self.lim[j]
+
+    def run(self):
+        self.first()
+        res = []
+        while not self.done():
+            m = "".join(self.msg)
+            res.append(m)
+            print m
+            self.next()
+        return res
+
+
+t = test("acbb")
+
+expected = [ 'aaaa', 'abaa', 'acaa', 'acba',
+             'aaba', 'abba', 'abbb', 'acbb',
+             'aabb', 'aaab', 'abab', 'acab' ]
+
+assert t.run() == expected