graph: let transitions() iterate only on valid transitions

This fixes #6.

* src/graph/graph.hh: Rename the old transitions() as
transition_vector(), and implement a new transitions() that iterates
only on non-dead transitions.
* src/tgba/tgbagraph.hh, src/tgba/tgbagraph.cc, src/graph/ngraph.hh:
Adjust wrappers.
* src/hoaparse/hoaparse.yy, src/tgbaalgos/complete.cc,
src/tgbaalgos/dtbasat.cc, src/tgbaalgos/dtgbasat.cc,
src/tgbaalgos/randomize.cc, src/tgbaalgos/safety.cc: Adjust calls.

src/graph/graph.hh

@@ -373,8 +373,121 @@ namespace spot
       transition t_;
     };
 
+    //////////////////////////////////////////////////
+    // all_trans
+    //////////////////////////////////////////////////
+
+    template <typename Graph>
+    class SPOT_API all_trans_iterator:
+      std::iterator<std::forward_iterator_tag,
+		    typename
+		    std::conditional<std::is_const<Graph>::value,
+				     const typename Graph::trans_storage_t,
+				     typename Graph::trans_storage_t>::type>
+    {
+      typedef
+	std::iterator<std::forward_iterator_tag,
+		      typename
+		      std::conditional<std::is_const<Graph>::value,
+				       const typename Graph::trans_storage_t,
+				       typename Graph::trans_storage_t>::type>
+	super;
+
+      typedef typename std::conditional<std::is_const<Graph>::value,
+					const typename Graph::trans_vector,
+					typename Graph::trans_vector>::type
+	tv_t;
+
+      unsigned t_;
+      tv_t& tv_;
+
+      void skip_()
+      {
+	unsigned s = tv_.size();
+	do
+	  ++t_;
+	while (t_ < s && tv_[t_].next_succ == t_);
       }
 
+    public:
+      all_trans_iterator(unsigned pos, tv_t& tv)
+	: t_(pos), tv_(tv)
+      {
+	skip_();
+      }
+
+      all_trans_iterator(tv_t& tv)
+	: t_(tv.size()), tv_(tv)
+      {
+      }
+
+      all_trans_iterator& operator++()
+      {
+	skip_();
+	return *this;
+      }
+
+      all_trans_iterator operator++(int)
+      {
+	all_trans_iterator old = *this;
+	++*this;
+	return old;
+      }
+
+      bool operator==(all_trans_iterator o) const
+      {
+	return t_ == o.t_;
+      }
+
+      bool operator!=(all_trans_iterator o) const
+      {
+	return t_ != o.t_;
+      }
+
+      typename super::reference
+      operator*()
+      {
+	return tv_[t_];
+      }
+
+      typename super::pointer
+      operator->()
+      {
+	return &tv_[t_];
+      }
+    };
+
+
+    template <typename Graph>
+    class SPOT_API all_trans
+    {
+      typedef typename std::conditional<std::is_const<Graph>::value,
+					const typename Graph::trans_vector,
+					typename Graph::trans_vector>::type
+	tv_t;
+      typedef all_trans_iterator<Graph> iter_t;
+      tv_t& tv_;
+    public:
+
+      all_trans(tv_t& tv)
+	: tv_(tv)
+      {
+      }
+
+      iter_t begin()
+      {
+	return {0, tv_};
+      }
+
+      iter_t end()
+      {
+	return {tv_};
+      }
+    };
+
+  }
+
+
   // The actual graph implementation
 
   template <typename State_Data, typename Trans_Data, bool Alternating>
@@ -614,12 +727,27 @@ namespace spot
       return states_;
     }
 
-    const trans_vector& transitions() const
+    internal::all_trans<const digraph> transitions() const
     {
       return transitions_;
     }
 
-    trans_vector& transitions()
+    internal::all_trans<digraph> transitions()
+    {
+      return transitions_;
+    }
+
+    // When using this method, beware that the first entry (transition
+    // #0) is not a real transition, and that any transition with
+    // next_succ pointing to itself is an erased transition.
+    //
+    // You should probably use transitions() instead.
+    const trans_vector& transition_vector() const
+    {
+      return transitions_;
+    }
+
+    trans_vector& transition_vector()
     {
       return transitions_;
     }

src/graph/ngraph.hh

@@ -91,7 +91,7 @@ namespace spot
 	  auto old = p.first->second;
 	  p.first->second = s;
 	  // Add the successor of OLD to those of S.
-	  auto& trans = g_.transitions();
+	  auto& trans = g_.transition_vector();
 	  auto& states = g_.states();
 	  trans[states[s].succ_tail].next_succ = states[old].succ;
 	  states[s].succ_tail = states[old].succ_tail;

src/hoaparse/hoaparse.yy

@@ -953,7 +953,7 @@ static void fix_acceptance(result_& r)
   // If a set x appears only as Inf(!x), we can complement it so that
   // we work with Inf(x) instead.
   auto onlyneg = r.neg_acc_sets - r.pos_acc_sets;
-  for (auto& t: r.h->aut->transitions())
+  for (auto& t: r.h->aut->transition_vector())
     t.acc ^= onlyneg;
 
   // However if set x is used elsewhere, for instance in
@@ -968,7 +968,7 @@ static void fix_acceptance(result_& r)
       auto v = acc.sets(both);
       auto vs = v.size();
       unsigned base = acc.add_sets(vs);
-      for (auto& t: r.h->aut->transitions())
+      for (auto& t: r.h->aut->transition_vector())
 	if ((t.acc & both) != both)
 	  for (unsigned i = 0; i < vs; ++i)
 	    if (!t.acc.has(i))

src/tgba/tgbagraph.cc

@@ -43,7 +43,7 @@ namespace spot
 			   // them.
 			 });
 
-    auto& trans = this->transitions();
+    auto& trans = this->transition_vector();
     unsigned tend = trans.size();
     unsigned out = 0;
     unsigned in = 1;

src/tgba/tgbagraph.hh

@@ -405,6 +405,11 @@ namespace spot
     auto transitions()
       SPOT_RETURN(g_.transitions());
 
+    auto transition_vector() const
+      SPOT_RETURN(g_.transition_vector());
+    auto transition_vector()
+      SPOT_RETURN(g_.transition_vector());
+
     auto is_dead_transition(const graph_t::trans_storage_t& t) const
       SPOT_RETURN(g_.is_dead_transition(t));
 

src/tgbaalgos/complete.cc

@@ -32,7 +32,7 @@ namespace spot
 	// acceptance set as the added sink would become accepting.
 	// In this case, add an acceptance set to all transitions.
 	allacc = aut->set_single_acceptance_set();
-	for (auto& t: aut->transitions())
+	for (auto& t: aut->transition_vector())
 	  t.acc = allacc;
       }
     else

src/tgbaalgos/dtbasat.cc

@@ -303,7 +303,6 @@ namespace spot
       // Compute the AP used in the hard way.
       bdd ap = bddtrue;
       for (auto& t: ref->transitions())
-	if (!ref->is_dead_transition(t))
 	ap &= bdd_support(t.cond);
 
       // Count the number of atomic propositions

src/tgbaalgos/dtgbasat.cc

@@ -432,7 +432,6 @@ namespace spot
       // Compute the AP used in the hard way.
       bdd ap = bddtrue;
       for (auto& t: ref->transitions())
-	if (!ref->is_dead_transition(t))
 	ap &= bdd_support(t.cond);
 
       // Count the number of atomic propositions

src/tgbaalgos/randomize.cc

@@ -42,9 +42,9 @@ namespace spot
       }
     if (randomize_transitions)
       {
-	auto begin = g.transitions().begin() + 1;
-	auto end = g.transitions().end();
-	std::random_shuffle(begin, end, spot::mrand);
+	g.remove_dead_transitions_();
+	auto& v = g.transition_vector();
+	std::random_shuffle(v.begin() + 1, v.end(), spot::mrand);
       }
 
     typedef tgba_digraph::graph_t::trans_storage_t tr_t;

src/tgbaalgos/safety.cc

@@ -66,7 +66,6 @@ namespace spot
   bool is_safety_mwdba(const const_tgba_digraph_ptr& aut)
   {
     for (auto& t: aut->transitions())
-      if (!aut->is_dead_transition(t))
       if (!aut->acc().accepting(t.acc))
 	return false;
     return true;