autfilt: add --is-alternating

* bin/autfilt.cc: Implement --is-alternating.
* tests/core/complete.test: Test it.
* NEWS: Mention it.

NEWS

@@ -11,7 +11,7 @@ New in spot 2.2.2.dev (Not yet released)
     alternating automata, but in any case they should display a
     diagnostic: if you see a crash, please report it.
 
-  * autfilt has a new --is-very-weak filter.
+  * autfilt has two new filters: --is-very-weak and --is-alternating.
 
   Library:
 

bin/autfilt.cc

@@ -102,15 +102,16 @@ enum {
   OPT_INCLUDED_IN,
   OPT_INHERENTLY_WEAK_SCCS,
   OPT_INTERSECT,
+  OPT_IS_ALTERNATING,
   OPT_IS_COMPLETE,
   OPT_IS_DETERMINISTIC,
   OPT_IS_EMPTY,
+  OPT_IS_INHERENTLY_WEAK,
   OPT_IS_STUTTER_INVARIANT,
   OPT_IS_TERMINAL,
   OPT_IS_UNAMBIGUOUS,
-  OPT_IS_WEAK,
-  OPT_IS_INHERENTLY_WEAK,
   OPT_IS_VERY_WEAK,
+  OPT_IS_WEAK,
   OPT_KEEP_STATES,
   OPT_MASK_ACC,
   OPT_MERGE,
@@ -182,6 +183,8 @@ static const argp_option options[] =
       "keep only inherently weak automata", 0 },
     { "is-very-weak", OPT_IS_VERY_WEAK, nullptr, 0,
       "keep only very-weak automata", 0 },
+    { "is-alternating", OPT_IS_ALTERNATING, nullptr, 0,
+      "keep only automata using universal branching", 0 },
     { "intersect", OPT_INTERSECT, "FILENAME", 0,
       "keep automata whose languages have an non-empty intersection with"
       " the automaton from FILENAME", 0 },
@@ -409,6 +412,7 @@ static struct opt_t
 }* opt;
 
 static bool opt_merge = false;
+static bool opt_is_alternating = false;
 static bool opt_is_complete = false;
 static bool opt_is_deterministic = false;
 static bool opt_is_unambiguous = false;
@@ -650,6 +654,9 @@ parse_opt(int key, char* arg, struct argp_state*)
     case OPT_INTERSECT:
       opt->intersect = read_automaton(arg, opt->dict);
       break;
+    case OPT_IS_ALTERNATING:
+      opt_is_alternating = true;
+      break;
     case OPT_IS_COMPLETE:
       opt_is_complete = true;
       break;
@@ -1016,6 +1023,8 @@ namespace
           matched &= opt_unused_ap_n.contains(unused);
           matched &= opt_used_ap_n.contains(aut->ap().size() - unused);
         }
+      if (matched && opt_is_alternating)
+        matched &= aut->is_alternating();
       if (matched && opt_is_complete)
         matched &= is_complete(aut);
       if (matched && (opt_sccs_set | opt_art_sccs_set))

tests/core/complete.test

@@ -227,3 +227,36 @@ EOF
 run 0 autfilt -CH automaton >out
 cat out
 diff out expected
+
+autfilt --is-alternating automaton >out
+cat out
+cat >expected <<EOF
+HOA: v1
+States: 2
+Start: 0
+AP: 2 "a" "b"
+acc-name: co-Buchi
+Acceptance: 1 Fin(0)
+properties: univ-branch trans-labels explicit-labels state-acc
+properties: deterministic very-weak
+--BODY--
+State: 0
+[!0 | 1] 0
+[0&!1] 0&1
+State: 1 {0}
+[0&!1] 1
+--END--
+HOA: v1
+States: 2
+Start: 0&1
+AP: 0
+acc-name: co-Buchi
+Acceptance: 1 Fin(0)
+properties: univ-branch trans-labels explicit-labels state-acc
+properties: deterministic
+--BODY--
+State: 0
+State: 1
+--END--
+EOF
+diff out expected