Replace the constant_term visitor by a flag in the formulae.

* src/ltlast/formula.hh (formula::accepts_eword): New method.
(formula::is.accepting_eword): New flag.
* src/ltlast/formula.cc (print_formula_props): Display the new
property.
* src/ltlast/atomic_prop.cc, src/ltlast/automatop.cc,
src/ltlast/binop.cc, src/ltlast/bunop.cc, src/ltlast/constant.cc,
src/ltlast/multop.cc, src/ltlast/unop.cc: Update
is.accepting_eword as appropriate.
* src/ltltest/consterm.cc, src/tgbaalgos/ltl2tgba_fm.cc: Adjust to
use accepts_eword().
* src/ltlvisit/consterm.cc, src/ltlvisit/consterm.hh: Delete.
* src/ltlvisit/Makefile.am: Remove these files.

src/ltlast/atomic_prop.cc

@@ -45,6 +45,7 @@ namespace spot
       is.eventual = false;
       is.universal = false;
       is.not_marked = true;
+      is.accepting_eword = false;
     }
 
     atomic_prop::~atomic_prop()

src/ltlast/automatop.cc

@@ -41,6 +41,7 @@ namespace spot
       is.eventual = false;
       is.universal = false;
       is.not_marked = true;
+      is.accepting_eword = false;
 
       unsigned s = v->size();
       for (unsigned i = 0; i < s; ++i)

src/ltlast/binop.cc

@@ -56,6 +56,7 @@ namespace spot
 	case Equiv:
 	  is.sugar_free_boolean = false;
 	  is.in_nenoform = false;
+	  is.accepting_eword = false;
 	  break;
 	case EConcatMarked:
 	  is.not_marked = false;
@@ -65,6 +66,7 @@ namespace spot
 	  is.ltl_formula = false;
 	  is.boolean = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case U:
 	  // 1 U a = Fa
@@ -72,6 +74,7 @@ namespace spot
 	    is.eventual = 1;
 	  is.boolean = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case W:
 	  // a W 0 = Ga
@@ -79,6 +82,7 @@ namespace spot
 	    is.universal = 1;
 	  is.boolean = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case R:
 	  // 0 R a = Ga
@@ -86,6 +90,7 @@ namespace spot
 	    is.universal = 1;
 	  is.boolean = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case M:
 	  // a M 1 = Fa
@@ -93,6 +98,7 @@ namespace spot
 	    is.eventual = 1;
 	  is.boolean = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	}
     }

src/ltlast/bunop.cc

@@ -35,16 +35,21 @@ namespace spot
     {
       props = child->get_props();
 
+      is.boolean = false;
+      is.ltl_formula = false;
+      is.eltl_formula = false;
+      is.eventual = false;
+      is.universal = false;
+
       switch (op_)
 	{
-	case Equal:
 	case Star:
+	  if (min_ == 0)
+	    is.accepting_eword = true;
+	  break;
+	case Equal:
 	case Goto:
-	  is.boolean = false;
+	  is.accepting_eword = (min_ == 0);
-	  is.ltl_formula = false;
-	  is.eltl_formula = false;
-	  is.eventual = false;
-	  is.universal = false;
 	  break;
 	}
     }

src/ltlast/constant.cc

@@ -51,6 +51,7 @@ namespace spot
 	  is.eventual = true;
 	  is.universal = true;
 	  is.not_marked = true;
+	  is.accepting_eword = false;
 	  break;
 	case constant::EmptyWord:
 	  is.boolean = false;
@@ -64,6 +65,7 @@ namespace spot
 	  is.eventual = false;
 	  is.universal = false;
 	  is.not_marked = true;
+	  is.accepting_eword = true;
 	  break;
 	}
     }

src/ltlast/formula.cc

@@ -86,6 +86,7 @@ namespace spot
       proprint(is_eventual, "e", "pure eventuality");
       proprint(is_universal, "u", "purely universal");
       proprint(is_marked, "+", "marked");
+      proprint(accepts_eword, "0", "accepts the empty word");
       return out;
     }
   }

src/ltlast/formula.hh

@@ -211,6 +211,12 @@ namespace spot
 	return !is.not_marked;
       }
 
+      /// Whether the formula accepts [*0].
+      bool accepts_eword() const
+      {
+	return is.accepting_eword;
+      }
+
       /// The properties as a field of bits.  For internal use.
       unsigned get_props() const
       {
@@ -252,7 +258,7 @@ namespace spot
 	// "the formula is".
 	bool boolean:1;		   // No temporal operators.
 	bool sugar_free_boolean:1; // Only AND, OR, and NOT operators.
-	bool in_nenoform:1;	   // Negative Normal Form
+	bool in_nenoform:1;	   // Negative Normal Form.
 	bool X_free:1;		   // No X operators.
 	bool sugar_free_ltl:1;	   // No F and G operators.
 	bool ltl_formula:1;	   // Only LTL operators.
@@ -260,7 +266,8 @@ namespace spot
 	bool psl_formula:1;	   // Only PSL operators.
 	bool eventual:1;	   // Purely eventual formula.
 	bool universal:1;	   // Purely universal formula.
-	bool not_marked:1;	   // No occurrence of EConcatMarked
+	bool not_marked:1;	   // No occurrence of EConcatMarked.
+	bool accepting_eword:1;	   // Accepts the empty word.
       };
       union
       {

src/ltlast/multop.cc

@@ -28,7 +28,6 @@
 #include "multop.hh"
 #include "constant.hh"
 #include "visitor.hh"
-#include "ltlvisit/consterm.hh"
 
 namespace spot
 {
@@ -40,10 +39,6 @@ namespace spot
       unsigned s = v->size();
       assert(s > 1);
 
-      props = (*v)[0]->get_props();
-      for (unsigned i = 1; i < s; ++i)
-	props &= (*v)[i]->get_props();
-
       switch (op)
 	{
 	case Concat:
@@ -53,15 +48,29 @@ namespace spot
 	  is.eltl_formula = false;
 	  is.eventual = false;
 	  is.universal = false;
-	  break;
+	  // fall through
 	case AndNLM:
 	  // The non-matching-length-And (&) can only appear in the
 	  // rational parts of PSL formula.  We don't remove the
 	  // Boolean flag, because applied to atomic propositions a&b
 	  // has the same effect as a&&b.
 	case And:
-	case Or:
+	  props = (*v)[0]->get_props();
+	  for (unsigned i = 1; i < s; ++i)
+	    props &= (*v)[i]->get_props();
 	  break;
+	case Or:
+	  {
+	    bool ew = (*v)[0]->accepts_eword();
+	    props = (*v)[0]->get_props();
+	    for (unsigned i = 1; i < s; ++i)
+	      {
+		ew |= (*v)[i]->accepts_eword();
+		props &= (*v)[i]->get_props();
+	      }
+	    is.accepting_eword = ew;
+	    break;
+	  }
 	}
     }
 
@@ -280,21 +289,20 @@ namespace spot
 		++i;
 	      }
 	  }
-	// We have    a* & [*0] & 0  = 0  // already checked above
+	// We have    a* & [*0] & c  = 0
-	//     but    a* & [*0] & c* = [*0]
+	//     and    a* & [*0] & c* = [*0]
-	// So if [*0] has been seen, check if all term recognize the
+	// So if [*0] has been seen, check if alls term recognize the
 	// empty word.
 	if (weak_abs_seen)
 	  {
-	    bool acc_empty = true;
+	    bool acc_eword = true;
 	    for (i = v->begin(); i != v->end(); ++i)
 	      {
-		if (acc_empty)
+		acc_eword &= (*i)->accepts_eword();
-		  acc_empty = constant_term_as_bool(*i);
 		(*i)->destroy();
 	      }
 	    delete v;
-	    if (acc_empty)
+	    if (acc_eword)
 	      return weak_abs;
 	    else
 	      return constant::false_instance();

src/ltlast/unop.cc

@@ -40,34 +40,40 @@ namespace spot
 	{
 	case Not:
 	  is.in_nenoform = !!dynamic_cast<atomic_prop*>(child);
+	  is.accepting_eword = false;
 	  break;
 	case X:
 	  is.boolean = false;
 	  is.X_free = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case F:
 	  is.boolean = false;
 	  is.eltl_formula = false;
 	  is.sugar_free_ltl = false;
 	  is.eventual = true;
+	  is.accepting_eword = false;
 	  break;
 	case G:
 	  is.boolean = false;
 	  is.eltl_formula = false;
 	  is.sugar_free_ltl = false;
 	  is.universal = true;
+	  is.accepting_eword = false;
 	  break;
 	case Finish:
 	  is.boolean = false;
 	  is.ltl_formula = false;
 	  is.psl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	case Closure:
 	case NegClosure:
 	  is.boolean = false;
 	  is.ltl_formula = false;
 	  is.eltl_formula = false;
+	  is.accepting_eword = false;
 	  break;
 	}
     }

src/ltltest/consterm.cc

@@ -22,7 +22,6 @@
 #include <cassert>
 #include <cstdlib>
 #include "ltlparse/public.hh"
-#include "ltlvisit/consterm.hh"
 #include "ltlast/allnodes.hh"
 
 void
@@ -44,7 +43,7 @@ main(int argc, char **argv)
   if (spot::ltl::format_parse_errors(std::cerr, argv[1], p1))
     return 2;
 
-  bool b = spot::ltl::constant_term_as_bool(f1);
+  bool b = f1->accepts_eword();
 
   std::cout << b << std::endl;
 
@@ -52,6 +51,7 @@ main(int argc, char **argv)
   assert(spot::ltl::atomic_prop::instance_count() == 0);
   assert(spot::ltl::unop::instance_count() == 0);
   assert(spot::ltl::binop::instance_count() == 0);
+  assert(spot::ltl::bunop::instance_count() == 0);
   assert(spot::ltl::multop::instance_count() == 0);
   return b;
 }

src/ltlvisit/Makefile.am

@@ -29,7 +29,6 @@ ltlvisitdir = $(pkgincludedir)/ltlvisit
 ltlvisit_HEADERS = \
   apcollect.hh \
   basicreduce.hh \
-  consterm.hh \
   contain.hh \
   clone.hh \
   destroy.hh \
@@ -51,7 +50,6 @@ noinst_LTLIBRARIES = libltlvisit.la
 libltlvisit_la_SOURCES = \
   apcollect.cc \
   basicreduce.cc \
-  consterm.cc \
   contain.cc \
   clone.cc \
   destroy.cc \

src/ltlvisit/consterm.cc

@@ -1,175 +0,0 @@
-// Copyright (C) 2010 Laboratoire de Recherche et Développement de
-// l'EPITA (LRDE).
-//
-// 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 2 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 Spot; see the file COPYING.  If not, write to the Free
-// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
-// 02111-1307, USA.
-
-#include "ltlvisit/consterm.hh"
-#include "ltlast/allnodes.hh"
-#include "ltlast/visitor.hh"
-
-namespace spot
-{
-  namespace ltl
-  {
-    namespace
-    {
-      class consterm_visitor: public const_visitor
-      {
-      public:
-	consterm_visitor() {}
-	virtual ~consterm_visitor() {}
-
-	bool result() const { return result_; }
-
-	void
-	visit(const atomic_prop*)
-	{
-	  result_ = false;
-	}
-
-	void
-	visit(const constant* c)
-	{
-	  result_ = (c == constant::empty_word_instance());
-	}
-
-	void
-	visit(const binop* bo)
-	{
-	  switch (bo->op())
-	    {
-	    case binop::Xor:
-	    case binop::Implies:
-	    case binop::Equiv:
-	      assert(!"const_term not yet defined on Xor, Implies and Equiv");
-	      break;
-	    case binop::U:
-	    case binop::W:
-	    case binop::M:
-	    case binop::R:
-	    case binop::EConcat:
-	    case binop::UConcat:
-	    case binop::EConcatMarked:
-	      assert(!"unsupported operator");
-	      break;
-	    }
-	}
-
-	void
-	visit(const bunop* bo)
-	{
-	  switch (bo->op())
-	    {
-	    case bunop::Star:
-	      if (bo->min() == 0)
-		result_ = true;
-	      else
-		bo->child()->accept(*this);
-	      break;
-	    case bunop::Equal:
-	    case bunop::Goto:
-	      result_ = bo->min() == 0;
-	      break;
-	    }
-	}
-
-	void
-	visit(const unop* uo)
-	{
-	  switch (uo->op())
-	    {
-	    case unop::Not:
-	      result_ = false;
-	      break;
-	    case unop::X:
-	    case unop::F:
-	    case unop::G:
-	    case unop::Finish:
-	    case unop::Closure:
-	    case unop::NegClosure:
-	      assert(!"unsupported operator");
-	      break;
-	    }
-	}
-
-	void
-	visit(const automatop*)
-	{
-	  assert(!"automatop not supported for constant term");
-	}
-
-	void
-	visit(const multop* mo)
-	{
-	  // The fusion operator cannot be used to recognize the empty word.
-	  if (mo->op() == multop::Fusion)
-	    {
-	      result_ = false;
-	      return;
-	    }
-
-	  unsigned max = mo->size();
-	  // This sets the initial value of result_.
-	  mo->nth(0)->accept(*this);
-
-	  for (unsigned n = 1; n < max; ++n)
-	    {
-	      bool r = constant_term_as_bool(mo->nth(n));
-
-	      switch (mo->op())
-		{
-		case multop::Or:
-		  result_ |= r;
-		  if (result_)
-		    return;
-		  break;
-		case multop::And:
-		case multop::AndNLM:
-		case multop::Concat:
-		  result_ &= r;
-		  if (!result_)
-		    return;
-		  break;
-		case multop::Fusion:
-		  /* Unreachable code */
-		  assert(0);
-		  break;
-		}
-	    }
-	}
-
-      private:
-	bool result_;
-      };
-
-    }
-
-    bool constant_term_as_bool(const formula* f)
-    {
-      consterm_visitor v;
-      f->accept(v);
-      return v.result();
-    }
-
-    formula* constant_term(const formula* f)
-    {
-      return constant_term_as_bool(f) ?
-	constant::empty_word_instance() : constant::false_instance();
-    }
-  }
-}

src/ltlvisit/consterm.hh

@@ -1,54 +0,0 @@
-// Copyright (C) 2010 Laboratoire de Recherche et Développement de
-// l'EPITA (LRDE).
-//
-// 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 2 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 Spot; see the file COPYING.  If not, write to the Free
-// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
-// 02111-1307, USA.
-
-#ifndef SPOT_LTLVISIT_CONSTERM_HH
-# define SPOT_LTLVISIT_CONSTERM_HH
-
-#include "ltlast/formula.hh"
-
-namespace spot
-{
-  namespace ltl
-  {
-    /// \brief Compute the constant term of a formula.
-    /// \ingroup ltl_misc
-    ///
-    /// The constant term of a formula is the empty word if the empty
-    /// word is a model of the formula, it is false otherwise.
-    ///
-    /// \see constant_term_as_bool
-    formula* constant_term(const formula* f);
-
-    /// \brief Compute the constant term of a formula.
-    /// \ingroup ltl_misc
-    ///
-    /// The constant term of a formula is the empty word if the empty
-    /// word is a model of the formula, it is false otherwise.
-    ///
-    /// This variant of the function return true instead of
-    /// constant::empty_word_instance() and false instead of
-    /// constant::false_instance().
-    ///
-    /// \see constant_term
-    bool constant_term_as_bool(const formula* f);
-  }
-}
-
-#endif // SPOT_LTLVISIT_LENGTH_HH

src/tgbaalgos/ltl2tgba_fm.cc

@@ -38,7 +38,6 @@
 #include <memory>
 #include "ltl2tgba_fm.hh"
 #include "ltlvisit/contain.hh"
-#include "ltlvisit/consterm.hh"
 #include "tgba/bddprint.hh"
 
 namespace spot
@@ -506,7 +505,7 @@ namespace spot
 		  for (unsigned n = 0; n < s; ++n)
 		    {
 		      const formula* f = node->nth(n);
-		      if (constant_term_as_bool(f))
+		      if (f->accepts_eword())
 			final->push_back(f->clone());
 		      else
 			non_final->push_back(f->clone());
@@ -593,12 +592,12 @@ namespace spot
 			      dest2->destroy();
 			      res_ |= label & bdd_ithvar(x);
 			    }
-			  if (constant_term_as_bool(node))
+			  if (node->accepts_eword())
 			    res_ |= label & next_to_concat();
 			}
 		    }
 		}
-	      if (constant_term_as_bool(node))
+	      if (node->accepts_eword())
 		res_ |= now_to_concat();
 
 	      break;
@@ -652,7 +651,7 @@ namespace spot
 		  bdd dest_bdd = bdd_existcomp(cube, dict_.next_set);
 		  formula* dest = dict_.conj_bdd_to_formula(dest_bdd);
 
-		  if (constant_term_as_bool(dest))
+		  if (dest->accepts_eword())
 		    {
 		      // The destination is a final state.  Make sure we
 		      // can also exit if tail is satisfied.
@@ -838,7 +837,7 @@ namespace spot
 	  case unop::Closure:
 	    {
 	      rat_seen_ = true;
-	      if (constant_term_as_bool(node->child()))
+	      if (node->child()->accepts_eword())
 		{
 		  res_ = bddtrue;
 		  return;
@@ -864,7 +863,7 @@ namespace spot
 						       dict_.var_set));
 
 		      const formula* dest2;
-		      if (constant_term_as_bool(dest))
+		      if (dest->accepts_eword())
 			{
 			  dest->destroy();
 			  res_ |= label;
@@ -891,7 +890,7 @@ namespace spot
 		      formula* dest = dict_.conj_bdd_to_formula(dest_bdd);
 
 		      const formula* dest2;
-		      if (constant_term_as_bool(dest))
+		      if (dest->accepts_eword())
 			{
 			  dest->destroy();
 			  res_ |= label;
@@ -915,7 +914,7 @@ namespace spot
 	      rat_seen_ = true;
 	      has_marked_ = true;
 
-	      if (constant_term_as_bool(node->child()))
+	      if (node->child()->accepts_eword())
 		{
 		  res_ = bddfalse;
 		  return;
@@ -945,7 +944,7 @@ namespace spot
 						   dict_.var_set));
 
 		  // !{ Exp } is false if Exp accepts the empty word.
-		  if (constant_term_as_bool(dest))
+		  if (dest->accepts_eword())
 		    {
 		      dest->destroy();
 		      continue;
@@ -1084,7 +1083,7 @@ namespace spot
 			  dest2->destroy();
 			  res_ |= label & bdd_ithvar(x);
 			}
-		      if (constant_term_as_bool(dest))
+		      if (dest->accepts_eword())
 			res_ |= label & f2;
 		    }
 		}
@@ -1112,7 +1111,7 @@ namespace spot
 			      dest2->destroy();
 			      res_ |= label & bdd_ithvar(x);
 			    }
-			  if (constant_term_as_bool(dest))
+			  if (dest->accepts_eword())
 			    res_ |= label & f2;
 			}
 		    }
@@ -1154,7 +1153,7 @@ namespace spot
 		      bdd udest =
 			bdd_ithvar(dict_.register_next_variable(dest2));
 
-		      if (constant_term_as_bool(dest))
+		      if (dest->accepts_eword())
 			udest &= f2;
 
 		      dest2->destroy();