* src/ltlvisit/nenoform.hh, src/ltlvisit/nenoform.cc: New files.

* src/ltlvisit/Makefile.am (libltlvisit_a_SOURCES): Add them.
* src/ltltest/equals.cc (main) [NENOFORM]: Call negative_normal_form.
* src/ltltest/nenoform.test, src/ltltest/tunenoform.test: New files.
* src/ltltest/Makefile.am (check_PROGRAMS): Add nenoform and
tunenoform.
(nenoform_SOURCES, nenoform_CPPFLAGS, tunenoform_SOURCES,
tunenoform_CPPFLAGS): New variables.
(TESTS): Add nenoform.test and tunenoform.test.

src/ltlvisit/nenoform.cc

@@ -0,0 +1,173 @@
+#include "nenoform.hh"
+#include "ltlast/allnodes.hh"
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    class negative_normal_form_visitor : public const_visitor
+    {
+    public:
+      negative_normal_form_visitor(bool negated)
+	: negated_(negated)
+      {
+      }
+
+      virtual 
+      ~negative_normal_form_visitor()
+      {
+      }
+
+      formula* result() const
+      {
+	return result_;
+      }
+      
+      void 
+      visit(const atomic_prop* ap)
+      {
+	formula* f = new atomic_prop(ap->name());
+	if (negated_)
+	  result_ = new unop(unop::Not, f);
+	else
+	  result_ = f;
+      }
+
+      void 
+      visit(const constant* c)
+      {
+	if (! negated_)
+	  {
+	    result_ = new constant(c->val());
+	    return;
+	  }
+
+	switch (c->val())
+	  {
+	  case constant::True:
+	    result_ = new constant(constant::False);
+	    return;
+	  case constant::False:
+	    result_ = new constant(constant::True);
+	    return;
+	  }
+	/* Unreachable code.  */
+	assert(0);
+      }
+
+      void 
+      visit(const unop* uo)
+      {
+	const formula* f = uo->child();
+	switch (uo->op())
+	  {
+	  case unop::Not:
+	    result_ = recurse_(f, negated_ ^ true);
+	    return;
+	  case unop::X:
+	    /* !Xa == X!a */
+	    result_ = new unop(unop::X, recurse(f));
+	    return;
+	  case unop::F:
+	    /* !Fa == G!a */
+	    result_ = new unop(negated_ ? unop::G : unop::F, recurse(f));
+	    return;
+	  case unop::G:
+	    /* !Ga == F!a */
+	    result_ = new unop(negated_ ? unop::F : unop::G, recurse(f));
+	    return;
+	  }
+	/* Unreachable code.  */
+	assert(0);
+      }
+
+      void 
+      visit(const binop* bo)
+      {
+	const formula* f1 = bo->first();
+	const formula* f2 = bo->second();
+	switch (bo->op())
+	  {
+	  case binop::Xor:
+	    /* !(a ^ b) == a <=> b */
+	    result_ = new binop(negated_ ? binop::Equiv : binop::Xor,
+				recurse_(f1, false), recurse_(f2, false));
+	    return;
+	  case binop::Equiv:
+	    /* !(a <=> b) == a ^ b */
+	    result_ = new binop(negated_ ? binop::Xor : binop::Equiv,
+				recurse_(f1, false), recurse_(f2, false));
+	    return;
+	  case binop::Implies:
+	    if (negated_)
+	      /* !(a => b) == a & !b */
+	      result_ = new multop(multop::And,
+				   recurse_(f1, false), recurse_(f2, true));
+	    else
+	      result_ = new binop(binop::Implies, recurse(f1), recurse(f2));
+	    return;
+	  case binop::U:
+	    /* !(a U b) == !a R !b */
+	    result_ = new binop(negated_ ? binop::R : binop::U,
+				recurse(f1), recurse(f2));
+	    return;
+	  case binop::R:
+	    /* !(a R b) == !a U !b */
+	    result_ = new binop(negated_ ? binop::U : binop::R,
+				recurse(f1), recurse(f2));
+	    return;
+	  }
+	/* Unreachable code.  */
+	assert(0);
+      }
+
+      void 
+      visit(const multop* mo)
+      {
+	/* !(a & b & c) == !a | !b | !c  */
+	/* !(a | b | c) == !a & !b & !c  */
+	multop::type op = mo->op();
+	if (negated_)
+	  switch (op)
+	    {
+	    case multop::And:
+	      op = multop::Or;
+	      break;
+	    case multop::Or:
+	      op = multop::And;
+	      break;
+	    }
+	multop* res = new multop(op);
+	unsigned mos = mo->size();
+	for (unsigned i = 0; i < mos; ++i)
+	  res->add(recurse(mo->nth(i)));
+	result_ = res;
+      }
+	
+      formula* 
+      recurse_(const formula* f, bool negated)
+      {
+	return negative_normal_form(f, negated);
+      }
+
+      formula* 
+      recurse(const formula* f)
+      {
+	return recurse_(f, negated_);
+      }
+      
+    protected:
+      formula* result_;
+      bool negated_;
+    };
+
+    formula* 
+    negative_normal_form(const formula* f, bool negated)
+    {
+      negative_normal_form_visitor v(negated);
+      f->accept(v);
+      return v.result();
+    }
+  }
+}