remove_fin: ignore more useless transitions

Do not clone transitions that are necessarily part of on accepting
cycle in the main copy of the automaton.

* spot/twaalgos/remfin.cc: Use propagate_marks_vector to ignore more
edges.
* tests/core/remfin.test, tests/python/remfin.py,
tests/python/automata.ipynb: Adjust.
* tests/sanity/style.test: Do not choke on C++17 if statements with
initializer.

NEWS

@@ -48,6 +48,9 @@ New in spot 2.9.3.dev  (not yet released)
   - Translations for formulas such as FGp1 & FGp2 &...& FGp32 which
     used to take ages are now instantaneous.  (See issue #412.)
 
+  - remove_fin() learned to remove more unnecessary edges by using
+    propagate_marks_vector().
+
   Bugs fixed:
 
   - Handle xor and <-> in a more natural way when translating

spot/twaalgos/remfin.cc

@@ -26,6 +26,7 @@
 #include <spot/twaalgos/isdet.hh>
 #include <spot/twaalgos/mask.hh>
 #include <spot/twaalgos/alternation.hh>
+#include <spot/twaalgos/degen.hh>
 
 // #define TRACE
 #ifdef TRACE
@@ -621,6 +622,17 @@ namespace spot
       bool sbacc = res->prop_state_acc().is_true();
       scc_info si(aut, scc_info_options::TRACK_STATES);
       unsigned nscc = si.scc_count();
+
+      // Help remove more useless transition by propagating marks.
+      auto propmarks = propagate_marks_vector(aut, &si);
+
+      // Edges that are already satisfying the acceptance of the
+      // main copy do not need to be duplicated in the clones, so
+      // we fill allacc_edge to remember those.  Of course this is
+      // only needed if the main copy can be accepting and if we
+      // will create clones.
+      std::vector<bool> allacc_edge(aut->edge_vector().size(), false);
+
       std::vector<unsigned> state_map(nst);
       for (unsigned n = 0; n < nscc; ++n)
         {
@@ -668,10 +680,11 @@ namespace spot
                   a = (t.acc & main_sets) | main_add;
                 res->new_edge(s, t.dst, t.cond, a);
                 // remember edges that are completely accepting
-                if (check_main_acc && main_acc.accepting(a))
-                  allacc_edge[aut->edge_number(t)] = true;
+                if (check_main_acc)
+                  if (unsigned en = aut->edge_number(t);
+                      main_acc.accepting(a | (propmarks[en] & main_sets)))
+                    allacc_edge[en] = true;
               }
-
           // We do not need any other copy if the SCC is non-accepting,
           // of if it does not intersect any Fin.
           if (!intersects_fin)
@@ -693,12 +706,16 @@ namespace spot
                     auto ns = state_map[s];
                     for (auto& t: aut->out(s))
                       {
-                        if ((t.acc & r) || si.scc_of(t.dst) != n
-                            // edges that are already accepting in the
-                            // main copy need not be copied in the
-                            // clone, since cycles going through them
-                            // are already accepted.
-                            || allacc_edge[aut->edge_number(t)])
+                        if (unsigned en = aut->edge_number(t);
+                            // Ignore edges have r, or that
+                            // necessarily go through r.
+                            ((t.acc | propmarks[en]) & r)
+                            // Ignore edges between SCCs.
+                            || si.scc_of(t.dst) != n
+                            // Ignore edges that are already accepting
+                            // in the main copy need not be copied in
+                            // the clone.
+                            || allacc_edge[en])
                           continue;
                         auto nd = state_map[t.dst];
                         res->new_edge(ns, nd, t.cond, (t.acc & k) | a);

tests/core/remfin.test

@@ -877,14 +877,12 @@ State: 0
 State: 1
 [2] 0
 [!2] 1
-[0&2] 2
 [0&!2] 3
 [2] 4
 [!2] 5
 State: 2
 [0] 2 {0 2}
 State: 3
-[0&2] 2 {0 2}
 [0&!2] 3 {0}
 State: 4
 [1 | 2] 4 {1 2}
@@ -1457,7 +1455,7 @@ State: 3
 [1] 3
 --END--
 HOA: v1
-States: 6
+States: 5
 Start: 0
 AP: 3 "a" "b" "c"
 acc-name: Buchi
@@ -1468,25 +1466,20 @@ State: 0
 [t] 0
 [!1&!2] 1
 [0] 2
-[1 | 2] 4
+[1 | 2] 3
 State: 1
 [2] 0
 [!2] 1
-[0&2] 2
-[0&!2] 3
-[2] 4
-[!2] 5
+[2] 3
+[!2] 4
 State: 2
 [0] 2 {0}
 State: 3
-[0&2] 2
-[0&!2] 3
+[1 | 2] 3 {0}
+[!1&!2] 4
 State: 4
-[1 | 2] 4 {0}
-[!1&!2] 5
-State: 5
-[2] 4 {0}
-[!2] 5
+[2] 3 {0}
+[!2] 4
 --END--
 EOF
 

tests/python/remfin.py

@@ -92,4 +92,4 @@ State: 2
 """)
 b = spot.remove_fin(a)
 size = (b.num_states(), b.num_edges())
-assert size == (5, 17);
+assert size == (5, 15);

tests/sanity/style.test

 #! /bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2009-2019 Laboratoire de Recherche et Développement de
+# Copyright (C) 2009-2020 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE).
 # Copyright (C) 2004, 2005 Laboratoire d'Informatique de Paris 6
 # (LIP6), département Systèmes Répartis Coopératifs (SRC), Université
@@ -158,7 +158,10 @@ for dir in "$TOP/spot" "$TOP/bin" "$TOP/tests"; do
       $GREP '[	 ]if ([^()]*).*{' $tmp &&
 	diag 'Opening { should be on its own line.'
 
-      $GREP '[	 ]if (.*).*;' $tmp &&
+      $GREP '[	 ]if ([^()]*).*;' $tmp &&
+	diag 'if body should be on another line.'
+
+      $GREP '[	 ]if ([^()]*([^()]*)[^()]*).*;' $tmp &&
 	diag 'if body should be on another line.'
 
       $GREP '[	 ]else.*;' $tmp &&