word: introduce use_all_aps()

This allows fixing issue #388 reported by Victor Khomenko.

* spot/twaalgos/word.cc, spot/twaalgos/word.hh (use_all_aps): New
method.
* tests/python/stutter-inv.ipynb: Use it.
* tests/python/stutter.py: New file, with Victor's test case.
* tests/Makefile.am: Add python/stutter.py.

tests/python/stutter.py

@@ -0,0 +1,47 @@
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2019 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/>.
+
+# Test that the spot.gen package works, in particular, we want
+# to make sure that the objects created from spot.gen methods
+# are usable with methods from the spot package.
+
+
+import spot
+
+def explain_stut(f):
+    f = spot.formula(f)
+    pos = spot.translate(f)
+    neg = spot.translate(spot.formula.Not(f))
+    word = spot.product(spot.closure(pos), spot.closure(neg)).accepting_word()
+    if word is None:
+        print(f, "is stutter invariant")
+        return
+    word.simplify()
+    # This line used to be missing, causing issue #388.
+    word.use_all_aps(pos.ap_vars())
+    waut = word.as_automaton()
+    aut = neg if waut.intersects(pos) else pos
+    word2 = spot.sl2(waut).intersecting_word(aut)
+    word2.simplify()
+    return(word, word2)
+
+# Test from issue #388
+w1, w2 = explain_stut('{(a:b) | (a;b)}|->Gc')
+assert str(w1) == 'a & !b & !c; cycle{!a & b & !c}'
+assert str(w2) == 'a & !b & !c; a & !b & !c; cycle{!a & b & !c}'