streett_to_generalized_buchi() now works on Streett-like

* NEWS: Mention the modification.
* spot/twaalgos/remfin.cc: Adapt to avoid infinite recursion.
* spot/twaalgos/totgba.cc: Work on Streett-like.
* tests/Makefile.am, tests/python/streett_totgba.py: Tests the
  modification.
* tests/core/remfin.test: Fix one test case that is now handled by
  the modification.

tests/python/streett_totgba.py

@@ -0,0 +1,84 @@
+#!/usr/bin/python3
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2017 Laboratoire de Recherche et Développement de
+# l'EPITA.
+#
+# 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/>.
+
+import spot
+import os
+import shutil
+import sys
+
+def parse_multiple_auts(hoa):
+  l = hoa.split('--END--')
+  a = []
+  cpt = 0
+  for x in l:
+    if x.isspace() or x == '':
+      continue
+    x = x + "--END--"
+    a.append(spot.automaton(x))
+
+  return a
+
+def ensure_deterministic(a):
+  if a.is_existential() and spot.is_deterministic(a):
+    return a
+
+  return a.postprocess('Generic', 'deterministic', 'Low')
+
+def equivalent(a1, a2):
+  na1 = spot.dualize(ensure_deterministic(a1))
+  na2 = spot.dualize(ensure_deterministic(a2))
+  return (not a1.intersects(na2)) and (not a2.intersects(na1))
+
+def tgba(a):
+  if not a.is_existential():
+    a = spot.remove_alternation(a)
+  a = spot.to_generalized_buchi(a)
+  return a
+
+def test_aut(aut):
+  stgba = tgba(aut)
+  assert equivalent(stgba, aut)
+  os.environ["SPOT_STREETT_CONV_MIN"] = '1'
+  sftgba = tgba(aut)
+  del os.environ["SPOT_STREETT_CONV_MIN"]
+  assert equivalent(stgba, sftgba)
+
+  slike = spot.simplify_acceptance(aut)
+
+  sltgba = tgba(slike)
+  os.environ["SPOT_STREETT_CONV_MIN"] = "1"
+  slftgba = tgba(slike)
+  del os.environ["SPOT_STREETT_CONV_MIN"]
+  assert equivalent(sltgba, slftgba)
+
+# Those automatons are generated with ltl2dstar, which is NOT part of spot,
+# using the following command:
+# genltl --eh-patterns --dac-patterns --hkrss-patterns --sb-patterns |\
+# ltldo "ltl2dstar --automata=streett --output-format=hoa\
+#       --ltl2nba=spin:ltl2tgba@-s %L ->%O" -F- --name=%f -H"
+
+if shutil.which('ltl2dstar') is None:
+  sys.exit(77)
+for a in spot.automata('genltl --eh-patterns --dac-patterns --hkrss-patterns\
+                        --sb-patterns |\
+                        ltldo "ltl2dstar --automata=streett --output-format=hoa\
+                        --ltl2nba=spin:ltl2tgba@-s %L ->%O"\
+                        -T5 -F- --name=%f -H|'):
+  test_aut(a)