autfilt: Add --is-terminal and --is-weak.

Fixes #47.

* src/twaalgos/strength.cc, src/twaalgos/strength.hh
(is_weak_automaton): New function.
(is_terminal_automaton): Generalize slightly.
* src/bin/autfilt.cc: Add options --is-terminal and --is-weak.
* src/tests/readsave.test: Add a test.
* NEWS: Update.

NEWS

 New in spot 1.99.5a (not yet released)
 
+  Command-line tools:
+
+  * autfilt has two now filters: --is-weak and --is-terminal.
+
   Library:
 
   * Properties of automata (like the "properties:" line of the HOA

src/bin/autfilt.cc

@@ -57,6 +57,7 @@
 #include "twaalgos/cleanacc.hh"
 #include "twaalgos/dtgbasat.hh"
 #include "twaalgos/complement.hh"
+#include "twaalgos/strength.hh"
 
 static const char argp_program_doc[] ="\
 Convert, transform, and filter omega-automata.\v\
@@ -85,6 +86,8 @@ enum {
   OPT_IS_DETERMINISTIC,
   OPT_IS_EMPTY,
   OPT_IS_UNAMBIGUOUS,
+  OPT_IS_TERMINAL,
+  OPT_IS_WEAK,
   OPT_KEEP_STATES,
   OPT_MASK_ACC,
   OPT_MERGE,
@@ -189,6 +192,10 @@ static const argp_option options[] =
       "keep automata with an empty language", 0 },
     { "is-unambiguous", OPT_IS_UNAMBIGUOUS, nullptr, 0,
       "keep only unambiguous automata", 0 },
+    { "is-terminal", OPT_IS_TERMINAL, nullptr, 0,
+      "keep only terminal automata", 0 },
+    { "is-weak", OPT_IS_WEAK, nullptr, 0,
+      "keep only weak automata", 0 },
     { "intersect", OPT_INTERSECT, "FILENAME", 0,
       "keep automata whose languages have an non-empty intersection with"
       " the automaton from FILENAME", 0 },
@@ -255,6 +262,8 @@ static bool opt_merge = false;
 static bool opt_is_complete = false;
 static bool opt_is_deterministic = false;
 static bool opt_is_unambiguous = false;
+static bool opt_is_terminal = false;
+static bool opt_is_weak = false;
 static bool opt_invert = false;
 static range opt_states = { 0, std::numeric_limits<int>::max() };
 static range opt_edges = { 0, std::numeric_limits<int>::max() };
@@ -365,6 +374,12 @@ parse_opt(int key, char* arg, struct argp_state*)
     case OPT_IS_UNAMBIGUOUS:
       opt_is_unambiguous = true;
       break;
+    case OPT_IS_TERMINAL:
+      opt_is_terminal = true;
+      break;
+    case OPT_IS_WEAK:
+      opt_is_weak = true;
+      break;
     case OPT_MERGE:
       opt_merge = true;
       break;
@@ -567,6 +582,10 @@ namespace
 	matched &= is_deterministic(aut);
       else if (opt_is_unambiguous)
 	matched &= is_unambiguous(aut);
+      if (opt_is_terminal)
+	matched &= is_terminal_automaton(aut);
+      else if (opt_is_weak)
+	matched &= is_weak_automaton(aut);
       if (opt->are_isomorphic)
         matched &= opt->isomorphism_checker->is_isomorphic(aut);
       if (opt_is_empty)

src/tests/readsave.test

@@ -51,6 +51,8 @@ EOF
 run 0 $autfilt --hoa input > stdout
 diff stdout input
 
+test `$autfilt -c --is-weak input` = 0
+
 # Transition merging
 cat >input <<\EOF
 HOA: v1
@@ -714,6 +716,9 @@ State: 2 {0 1} [0] 2
 --END--
 EOF
 
+test `$autfilt --is-weak -c input4` = 1
+test `$autfilt --is-terminal -c input4` = 0
+
 $autfilt -H --small --high input4 >output4
 $autfilt -H --small input4 >output4b
 $autfilt -H --high input4 >output4c
@@ -742,6 +747,12 @@ diff output4b expect4
 diff output4c expect4
 
 $autfilt -Hv --small input4 >output5
+test `$autfilt --is-weak -c output4` = 1
+test `$autfilt --is-terminal -c output4` = 0
+
+sed 's/\[0\]/[t]/g' expect4 > output4d
+test `$autfilt --is-terminal -c output4d` = 1
+
 
 cat >expect5<<EOF
 HOA: v1

src/twaalgos/strength.cc

@@ -19,49 +19,68 @@
 
 #include "strength.hh"
 #include "misc/hash.hh"
+#include "isweakscc.hh"
 #include <deque>
 
 namespace spot
 {
-  bool
-  is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* si)
+  namespace
   {
-    if (aut->prop_terminal())
-      return true;
-    // Create an scc_info if the user did not give one to us.
-    bool need_si = !si;
-    if (need_si)
-      si = new scc_info(aut);
-    si->determine_unknown_acceptance();
+    template <bool terminal>
+    bool is_type_automaton(const const_twa_graph_ptr& aut, scc_info* si)
+    {
+      // Create an scc_info if the user did not give one to us.
+      bool need_si = !si;
+      if (need_si)
+	si = new scc_info(aut);
+      si->determine_unknown_acceptance();
 
-    bool result = true;
+      bool result = true;
+      unsigned n = si->scc_count();
+      for (unsigned i = 0; i < n; ++i)
+	{
+	  if (si->is_trivial(i))
+	    continue;
+	  bool first = true;
+	  acc_cond::mark_t m = 0U;
+	  for (auto src: si->states_of(i))
+	    for (auto& t: aut->out(src))
+	      if (si->scc_of(t.dst) == i)
+		{
+		  if (first)
+		    {
+		      first = false;
+		      m = t.acc;
+		    }
+		  else if (m != t.acc)
+		    {
+		      result = false;
+		      goto exit;
+		    }
+		}
+	  if (terminal && si->is_accepting_scc(i) && !is_complete_scc(*si, i))
+	    {
+	      result = false;
+	      break;
+	    }
+	}
+    exit:
+      if (need_si)
+	delete si;
+      return result;
+    }
+  }
 
-    for (auto& scc: *si)
-      {
-	if (scc.is_rejecting())
-	  continue;
-	// Accepting SCCs should have only one state.
-	auto& st = scc.states();
-	if (st.size() != 1)
-	  {
-	    result = false;
-	    break;
-	  }
-	// The state should have only one edge that is a
-	// self-loop labelled by true.
-	auto src = st.front();
-	auto out = aut->out(src);
-	auto it = out.begin();
-	assert(it != out.end());
-	result =
-	  (it->cond == bddtrue) && (it->dst == src) && (++it == out.end());
-	if (!result)
-	  break;
-      }
+  bool
+  is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* si)
+  {
+    return aut->prop_terminal() || is_type_automaton<true>(aut, si);
+  }
 
-    if (need_si)
-      delete si;
-    return result;
+  bool
+  is_weak_automaton(const const_twa_graph_ptr& aut, scc_info* si)
+  {
+    return aut->prop_weak() || is_type_automaton<false>(aut, si);
   }
 
   bool is_safety_mwdba(const const_twa_graph_ptr& aut)

src/twaalgos/strength.hh

@@ -25,9 +25,8 @@ namespace spot
 {
   /// \brief Whether an automaton is terminal.
   ///
-  /// An automaton is terminal if any accepting path ends on an
-  /// accepting state with only one transition that is a self-loop
-  /// labelled by true.
+  /// An automaton is terminal if it is weak, and all accepting SCCs
+  /// are complete.
   ///
   /// \param aut the automaton to check
   ///
@@ -36,6 +35,19 @@ namespace spot
   SPOT_API bool
   is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* sm = nullptr);
 
+
+  /// \brief Whether an automaton is weak.
+  ///
+  /// An automaton is weak if if any given SCC, all transitions belong
+  /// to the same acceptance sets.
+  ///
+  /// \param aut the automaton to check
+  ///
+  /// \param sm an scc_info object for the automaton if available (it
+  /// will be built otherwise).
+  SPOT_API bool
+  is_weak_automaton(const const_twa_graph_ptr& aut, scc_info* sm = nullptr);
+
   /// \brief Whether a minimized WDBA represents a safety property.
   ///
   /// A minimized WDBA (as returned by a successful run of