twaalgos: implement restrict_dead_end_edges_here()

Discussed in issue #587.

* spot/twaalgos/deadends.cc, spot/twaalgos/deadends.hh: New files.
* spot/twaalgos/Makefile.am, python/spot/impl.i: Add them.
* tests/core/deadends.test, tests/python/deadends.py: New files.
* tests/Makefile.am: Add them.
* spot/twa/acc.cc, spot/twa/acc.hh (keep_one_inf_per_branch): New
method.
* bin/autfilt.cc: Learn option --restrict-dead-end-edges.
* NEWS: Mention it.

tests/python/deadends.py

@@ -0,0 +1,158 @@
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) by the Spot authors, see the AUTHORS file for details.
+#
+# 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
+from unittest import TestCase
+tc = TestCase()
+
+b = spot.translate('FGb')
+a = spot.translate('GFa & GFc')
+p = spot.product_susp(b, a)
+q = spot.scc_filter(spot.simulation(p), True)
+s = p.to_str()
+spot.restrict_dead_end_edges_here(p)
+s += p.to_str()
+# Applying it twice should not change anything
+spot.restrict_dead_end_edges_here(p)
+s += p.to_str()
+
+tc.assertEqual(s, """HOA: v1
+States: 2
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+--END--HOA: v1
+States: 2
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[0&1&!2] 1 {0}
+[0&1&2] 1 {0 1}
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+--END--HOA: v1
+States: 2
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[0&1&!2] 1 {0}
+[0&1&2] 1 {0 1}
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+--END--""")
+
+spot.restrict_dead_end_edges_here(q)
+s = q.to_str()
+tc.assertEqual(s, """HOA: v1
+States: 2
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[0&1] 1
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+--END--""")
+
+a = spot.translate('GFa & (FGb | FGc) & GFc')
+s = a.to_str()
+spot.restrict_dead_end_edges_here(a)
+s += a.to_str()
+tc.assertEqual(s, """HOA: v1
+States: 3
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[0&1 | 1&2] 1
+[2] 2
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+State: 2
+[!0&2] 2 {1}
+[0&2] 2 {0 1}
+--END--HOA: v1
+States: 3
+Start: 0
+AP: 3 "a" "b" "c"
+acc-name: generalized-Buchi 2
+Acceptance: 2 Inf(0)&Inf(1)
+properties: trans-labels explicit-labels trans-acc stutter-invariant
+--BODY--
+State: 0
+[t] 0
+[0&1] 1
+[0&2] 2
+State: 1
+[!0&1&!2] 1
+[0&1&!2] 1 {0}
+[!0&1&2] 1 {1}
+[0&1&2] 1 {0 1}
+State: 2
+[!0&2] 2 {1}
+[0&2] 2 {0 1}
+--END--""")