python: improve bdd_dict bindings

Fixes #372.

* python/spot/impl.i: Refactor the handling of exceptions using a
Lippincott function.  Map out_of_range to IndexError.  Add
PyObject* version for bdd_dict's register and unregister functions
so we can use Python objects as well.
* tests/python/bdddict.py: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the changes.

tests/python/bdddict.py

@@ -0,0 +1,119 @@
+# -*- 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/>.
+
+# Make sure we can leep track of BDD association in Python using bdd_dict, as
+# discussed in issue #372.
+
+class bdd_holder:
+    def __init__(self, aut):
+        self.bdddict = d = aut.get_dict()
+        for ap in aut.ap():
+            d.register_proposition(ap, self)
+
+    def __del__(self):
+        self.bdddict.unregister_all_my_variables(self)
+
+
+class bdd_holder2:
+    def __init__(self, aut):
+        self.bdddict = d = aut.get_dict()
+        d.register_all_variables_of(aut, self)
+
+    def __del__(self):
+        self.bdddict.unregister_all_my_variables(self)
+
+
+class bdd_holder3:
+    def __init__(self, h2):
+        self.bdddict = d = h2.bdddict
+        d.register_all_variables_of(h2, self)
+
+    def __del__(self):
+        self.bdddict.unregister_all_my_variables(self)
+
+
+
+def check_ok():
+    assert type(bdict.varnum(spot.formula.ap("a"))) is int
+
+def check_nok():
+    try:
+        bdict.varnum(spot.formula.ap("a"))
+    except IndexError as e:
+        pass
+    else:
+        raise RuntimeError("missing exception")
+
+def debug(txt):
+    # print(txt)
+    # bdict.dump(spot.get_cout())
+    pass
+
+import spot
+aut = spot.translate("a U b")
+bdict = aut.get_dict()
+debug("aut")
+
+word = aut.accepting_word()
+debug("word")
+check_ok()
+
+h = bdd_holder(aut)
+debug("h")
+check_ok()
+
+h2 = bdd_holder2(aut)
+debug("h2")
+check_ok()
+
+del aut
+debug("-aut")
+check_ok()
+
+del word
+debug("-word")
+check_ok()
+
+del h
+debug("-h")
+check_ok()
+
+del h2
+debug("-h2")
+check_nok()
+
+h2 = bdd_holder2(spot.translate("a U b").accepting_word())
+debug("h2")
+h3 = bdd_holder3(h2)
+var = bdict.register_anonymous_variables(1, h3)
+debug("h3")
+assert var == 2
+del h2
+debug("-h2")
+check_ok()
+del h3
+debug("-h3")
+check_nok()
+
+h2 = bdd_holder2(spot.translate("a U b").accepting_word())
+debug("h2")
+bdict.unregister_variable(bdict.varnum("b"), h2)
+bdict.unregister_variable(bdict.varnum("a"), h2)
+debug("-b,-a")
+check_nok()