genem: fix removal of unsatisfied Fin(x) sets

Fixes #360.

* spot/twa/acc.cc, spot/twa/acc.hh (force_inf): New method.
* spot/twaalgos/genem.cc: Fix the emptiness check using force_inf.
* tests/python/genem.py: Add test case and adjust the python
version of the emptiness check.

spot/twa/acc.cc

@@ -1481,6 +1481,51 @@ namespace spot
       SPOT_UNREACHABLE();
       return {};
     }
+
+    static acc_cond::acc_code
+    force_inf_rec(const acc_cond::acc_word* pos, acc_cond::mark_t rem)
+    {
+      auto start = pos - pos->sub.size;
+      switch (pos->sub.op)
+        {
+        case acc_cond::acc_op::And:
+          {
+            --pos;
+            auto res = acc_cond::acc_code::t();
+            do
+              {
+                auto tmp = force_inf_rec(pos, rem) & std::move(res);
+                std::swap(tmp, res);
+                pos -= pos->sub.size + 1;
+              }
+            while (pos > start);
+            return res;
+          }
+        case acc_cond::acc_op::Or:
+          {
+            --pos;
+            auto res = acc_cond::acc_code::f();
+            do
+              {
+                auto tmp = force_inf_rec(pos, rem) | std::move(res);
+                std::swap(tmp, res);
+                pos -= pos->sub.size + 1;
+              }
+            while (pos > start);
+            return res;
+          }
+        case acc_cond::acc_op::Fin:
+          return acc_cond::acc_code::fin(pos[-1].mark - rem);
+        case acc_cond::acc_op::Inf:
+          return acc_cond::acc_code::inf(pos[-1].mark);
+        case acc_cond::acc_op::FinNeg:
+        case acc_cond::acc_op::InfNeg:
+          SPOT_UNREACHABLE();
+          return {};
+        }
+      SPOT_UNREACHABLE();
+      return {};
+    }
   }
 
   acc_cond::acc_code
@@ -1499,6 +1544,14 @@ namespace spot
     return strip_rec(&back(), rem, missing, false);
   }
 
+  acc_cond::acc_code
+  acc_cond::acc_code::force_inf(mark_t rem) const
+  {
+    if (is_t() || is_f())
+      return *this;
+    return force_inf_rec(&back(), rem);
+  }
+
   acc_cond::mark_t
   acc_cond::acc_code::used_sets() const
   {

spot/twa/acc.hh

@@ -921,6 +921,8 @@ namespace spot
       acc_code remove(acc_cond::mark_t rem, bool missing) const;
       // Same as remove, but also shift numbers
       acc_code strip(acc_cond::mark_t rem, bool missing) const;
+      // for all x in m, this replaces Fin(x) by false.
+      acc_code force_inf(mark_t m) const;
 
       // Return the set of sets appearing in the condition.
       acc_cond::mark_t used_sets() const;
@@ -1388,6 +1390,12 @@ namespace spot
         { num_sets() - (all_sets() & rem).count(), code_.strip(rem, missing) };
     }
 
+    // For all x in m, this replaces Fin(x) by false.
+    acc_cond force_inf(mark_t m) const
+    {
+      return {num_sets(), code_.force_inf(m)};
+    }
+
     // Restrict an acceptance condition to a subset of set numbers
     // that are occurring at some point.
     acc_cond restrict_to(mark_t rem) const

spot/twaalgos/genem.cc

@@ -175,7 +175,7 @@ namespace spot
            <deal_with_disjunct>))
         return false;
       // Try to accept when Fin(fo) == false
-      tmp.set(acc.remove({(unsigned) fo}, false));
+      tmp.set(acc.force_inf({(unsigned) fo}));
       return generic_emptiness_check_for_scc_nocopy
         <deal_with_disjunct>(si, scc, tocut);
       return true;

tests/python/genem.py

@@ -106,6 +106,30 @@ HOA: v1 States: 2 Acceptance: 6 (Fin(0)|Fin(1))&(Fin(2)|Fin(3))&
 (Fin(4)|Fin(5)) Start: 0 AP: 0 --BODY-- State: 0 [t] 0 {0 2 3} [t]
 1 {1 4} State: 1 [t] 0 {2 5} [t] 1 {3 0 1} --END--""")
 
+# From issue #360.
+a360 = spot.automaton("""HOA: v1
+States: 2
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 8 Fin(5) & (Inf(4) | (Fin(3) & (Inf(2) | (Fin(1) & Inf(0))))) &
+              (Inf(6) | Inf(7)) & (Fin(6)|Fin(7))
+properties: trans-labels explicit-labels trans-acc complete
+properties: deterministic
+--BODY--
+State: 0
+[0&1] 0 {4 6 7}
+[0&!1] 1 {0 6}
+[!0&1] 0 {3 7}
+[!0&!1] 0 {0}
+State: 1
+[0&1] 0 {4 6 7}
+[0&!1] 1 {3 6}
+[!0&1] 0 {4 7}
+[!0&!1] 1 {0}
+--END--""")
+
+
+
 
 def generic_emptiness2_rec(aut):
     spot.cleanup_acceptance_here(aut, False)
@@ -143,7 +167,7 @@ def generic_emptiness2_rec(aut):
                     if not generic_emptiness2(part):
                         return False
                 whole = si.split_on_sets(scc, [])[0]
-                whole.set_acceptance(acc.remove([fo], False))
+                whole.set_acceptance(acc.force_inf([fo]))
                 if not generic_emptiness2(whole):
                     return False
     return True
@@ -166,4 +190,4 @@ def run_bench(automata):
         print(res)
         assert res in ('TTT', 'FFF')
 
-run_bench([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a11])
+run_bench([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a11, a360])