]> Dogcows Code - chaz/yoink/blobdiff - src/Moof/stlplus/digraph.tpp
initial working frustum culling implementation
[chaz/yoink] / src / Moof / stlplus / digraph.tpp
diff --git a/src/Moof/stlplus/digraph.tpp b/src/Moof/stlplus/digraph.tpp
new file mode 100755 (executable)
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--- /dev/null
@@ -0,0 +1,1483 @@
+////////////////////////////////////////////////////////////////////////////////\r
+\r
+//   Author:    Andy Rushton\r
+//   Copyright: (c) Southampton University 1999-2004\r
+//              (c) Andy Rushton           2004-2009\r
+//   License:   BSD License, see ../docs/license.html\r
+\r
+//   Note: I tried to write this using STL lists for the node and arc lists, but\r
+//   it got far too hairy. The specific problem is that I wanted a digraph\r
+//   iterator to contain a list::iterator so I needed to be able to generate a\r
+//   list::iterator from a node or arc and STL list iterators don't give you that\r
+//   functionality. I tried burgling the data structures, but that was\r
+//   non-portable between different STL implementations so needed lots of #ifdefs\r
+//   and so was mind-bogglingly awful and unreadable - in other words a\r
+//   maintenance nightmare. I gave up and impemented my own lists - not difficult.\r
+\r
+//   I use circular double-linked lists. The circular design means that both\r
+//   ends of the list are equally accessible in unit time. An empty list\r
+//   contains no objects. There is no end node in the list - unlike the STL\r
+//   lists which have a dummy node for end iterators to point to -\r
+//   conceptually the end iterator points one element beyond the end of the\r
+//   list. However, I implement the end iterator concept in the iterator\r
+//   itself, so do not need the dummy end node.\r
+\r
+////////////////////////////////////////////////////////////////////////////////\r
+#include <algorithm>\r
+#include <deque>\r
+\r
+////////////////////////////////////////////////////////////////////////////////\r
+// Internals\r
+\r
+namespace stlplus\r
+{\r
+\r
+  template<typename NT, typename AT>\r
+  class digraph_node\r
+  {\r
+  public:\r
+    master_iterator<digraph<NT,AT>, digraph_node<NT,AT> > m_master;\r
+    NT m_data;\r
+    digraph_node<NT,AT>* m_prev;\r
+    digraph_node<NT,AT>* m_next;\r
+    std::vector<digraph_arc<NT,AT>*> m_inputs;\r
+    std::vector<digraph_arc<NT,AT>*> m_outputs;\r
+  public:\r
+    digraph_node(const digraph<NT,AT>* owner, const NT& d = NT()) :\r
+      m_master(owner,this), m_data(d), m_prev(0), m_next(0)\r
+      {\r
+      }\r
+    ~digraph_node(void)\r
+      {\r
+      }\r
+  };\r
+\r
+  template<typename NT, typename AT>\r
+  class digraph_arc\r
+  {\r
+  public:\r
+    master_iterator<digraph<NT,AT>, digraph_arc<NT,AT> > m_master;\r
+    AT m_data;\r
+    digraph_arc<NT,AT>* m_prev;\r
+    digraph_arc<NT,AT>* m_next;\r
+    digraph_node<NT,AT>* m_from;\r
+    digraph_node<NT,AT>* m_to;\r
+    digraph_arc(const digraph<NT,AT>* owner, digraph_node<NT,AT>* from = 0, digraph_node<NT,AT>* to = 0, const AT& d = AT()) : \r
+      m_master(owner,this), m_data(d), m_prev(0), m_next(0), m_from(from), m_to(to)\r
+      {\r
+      }\r
+  };\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Iterators\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Node iterator\r
+\r
+  // construct a null iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_iterator<NT,AT,NRef,NPtr>::digraph_iterator(void)\r
+  {\r
+  }\r
+\r
+  // valid iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_iterator<NT,AT,NRef,NPtr>::digraph_iterator(digraph_node<NT,AT>* node) :\r
+    safe_iterator<digraph<NT,AT>,digraph_node<NT,AT> >(node->m_master)\r
+  {\r
+  }\r
+\r
+  // end iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_iterator<NT,AT,NRef,NPtr>::digraph_iterator(const digraph<NT,AT>* owner) :\r
+    safe_iterator<digraph<NT,AT>,digraph_node<NT,AT> >(owner)\r
+  {\r
+  }\r
+\r
+  // alias an iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_iterator<NT,AT,NRef,NPtr>::digraph_iterator(const safe_iterator<digraph<NT,AT>, digraph_node<NT,AT> >& iterator) : \r
+    safe_iterator<digraph<NT,AT>,digraph_node<NT,AT> >(iterator)\r
+  {\r
+  }\r
+\r
+  // destructor\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_iterator<NT,AT,NRef,NPtr>::~digraph_iterator(void)\r
+  {\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::const_iterator digraph_iterator<NT,AT,NRef,NPtr>::constify (void) const\r
+  {\r
+    return digraph_iterator<NT,AT,const NT&,const NT*>(*this);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::iterator digraph_iterator<NT,AT,NRef,NPtr>::deconstify (void) const\r
+  {\r
+    return digraph_iterator<NT,AT,NT&,NT*>(*this);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator& digraph_iterator<NT,AT,NRef,NPtr>::operator ++ (void)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    if (this->node()->m_next)\r
+      this->set(this->node()->m_next->m_master);\r
+    else\r
+      this->set_end();\r
+    return *this;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator digraph_iterator<NT,AT,NRef,NPtr>::operator ++ (int)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    // post-increment is defined in terms of the pre-increment\r
+    digraph_iterator<NT,AT,NRef,NPtr> result(*this);\r
+    ++(*this);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator& digraph_iterator<NT,AT,NRef,NPtr>::operator -- (void)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    if (this->node()->m_prev)\r
+      this->set(this->node()->m_prev->m_master);\r
+    else\r
+      this->set_end();\r
+    return *this;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator digraph_iterator<NT,AT,NRef,NPtr>::operator -- (int)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    // post-decrement is defined in terms of the pre-decrement\r
+    digraph_iterator<NT,AT,NRef,NPtr> result(*this);\r
+    --(*this);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  bool digraph_iterator<NT,AT,NRef,NPtr>::operator == (const TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator& r) const\r
+  {\r
+    return equal(r);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  bool digraph_iterator<NT,AT,NRef,NPtr>::operator != (const TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator& r) const\r
+  {\r
+    return !operator==(r);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  bool digraph_iterator<NT,AT,NRef,NPtr>::operator < (const TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::this_iterator& r) const\r
+  {\r
+    return compare(r) < 0;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::reference digraph_iterator<NT,AT,NRef,NPtr>::operator*(void) const\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    return this->node()->m_data;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_iterator<NT,AT,NRef,NPtr>::pointer digraph_iterator<NT,AT,NRef,NPtr>::operator->(void) const\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    return &(operator*());\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Arc Iterator\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  digraph_arc_iterator<NT,AT,ARef,APtr>::digraph_arc_iterator(void)\r
+  {\r
+  }\r
+\r
+  // valid iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_arc_iterator<NT,AT,NRef,NPtr>::digraph_arc_iterator(digraph_arc<NT,AT>* arc) :\r
+    safe_iterator<digraph<NT,AT>,digraph_arc<NT,AT> >(arc->m_master)\r
+  {\r
+  }\r
+\r
+  // end iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_arc_iterator<NT,AT,NRef,NPtr>::digraph_arc_iterator(const digraph<NT,AT>* owner) :\r
+    safe_iterator<digraph<NT,AT>,digraph_arc<NT,AT> >(owner)\r
+  {\r
+  }\r
+\r
+  // alias an iterator\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  digraph_arc_iterator<NT,AT,NRef,NPtr>::digraph_arc_iterator(const safe_iterator<digraph<NT,AT>, digraph_arc<NT,AT> >& iterator) : \r
+    safe_iterator<digraph<NT,AT>,digraph_arc<NT,AT> >(iterator)\r
+  {\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  digraph_arc_iterator<NT,AT,ARef,APtr>::~digraph_arc_iterator(void)\r
+  {\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,NRef,NPtr>::const_iterator digraph_arc_iterator<NT,AT,NRef,NPtr>::constify (void) const\r
+  {\r
+    return digraph_arc_iterator<NT,AT,const AT&,const AT*>(*this);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename NRef, typename NPtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,NRef,NPtr>::iterator digraph_arc_iterator<NT,AT,NRef,NPtr>::deconstify (void) const\r
+  {\r
+    return digraph_arc_iterator<NT,AT,AT&,AT*>(*this);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator& digraph_arc_iterator<NT,AT,ARef,APtr>::operator ++ (void)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    if (this->node()->m_next)\r
+      this->set(this->node()->m_next->m_master);\r
+    else\r
+      this->set_end();\r
+    return *this;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator digraph_arc_iterator<NT,AT,ARef,APtr>::operator ++ (int)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    // post-increment is defined in terms of the pre-increment\r
+    digraph_arc_iterator<NT,AT,ARef,APtr> result(*this);\r
+    ++(*this);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator& digraph_arc_iterator<NT,AT,ARef,APtr>::operator -- (void)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    if (this->node()->m_prev)\r
+      this->set(this->node()->m_prev->m_master);\r
+    else\r
+      this->set_end();\r
+    return *this;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator digraph_arc_iterator<NT,AT,ARef,APtr>::operator -- (int)\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    // post-decrement is defined in terms of the pre-decrement\r
+    digraph_arc_iterator<NT,AT,ARef,APtr> result(*this);\r
+    --(*this);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  bool digraph_arc_iterator<NT,AT,ARef,APtr>::operator == (const TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator& r) const\r
+  {\r
+    return equal(r);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  bool digraph_arc_iterator<NT,AT,ARef,APtr>::operator != (const TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator& r) const\r
+  {\r
+    return !operator==(r);\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  bool digraph_arc_iterator<NT,AT,ARef,APtr>::operator < (const TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::this_iterator& r) const\r
+  {\r
+    return compare(r) < 0;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::reference digraph_arc_iterator<NT,AT,ARef,APtr>::operator*(void) const\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    this->assert_valid();\r
+    return this->node()->m_data;\r
+  }\r
+\r
+  template<typename NT, typename AT, typename ARef, typename APtr>\r
+  TYPENAME digraph_arc_iterator<NT,AT,ARef,APtr>::pointer digraph_arc_iterator<NT,AT,ARef,APtr>::operator->(void) const\r
+    throw(null_dereference,end_dereference)\r
+  {\r
+    return &(operator*());\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // subtype utilities\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_vector digraph<NT,AT>::constify_arcs(const TYPENAME digraph<NT,AT>::arc_vector& arcs) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > result;\r
+    for (unsigned i = 0; i < arcs.size(); i++)\r
+    {\r
+      arcs[i].assert_valid(this);\r
+      result.push_back(arcs[i].constify());\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_vector digraph<NT,AT>::deconstify_arcs(const TYPENAME digraph<NT,AT>::const_arc_vector& arcs) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_arc_iterator<NT,AT,AT&,AT*> > result;\r
+    for (unsigned i = 0; i < arcs.size(); i++)\r
+    {\r
+      arcs[i].assert_valid(this);\r
+      result.push_back(arcs[i].deconstify());\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_path_vector digraph<NT,AT>::constify_paths(const TYPENAME digraph<NT,AT>::path_vector& paths) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > result;\r
+    for (unsigned i = 0; i < paths.size(); i++)\r
+      result.push_back(constify_arcs(paths[i]));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::path_vector digraph<NT,AT>::deconstify_paths(const TYPENAME digraph<NT,AT>::const_path_vector& paths) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<std::vector<digraph_arc_iterator<NT,AT,AT&,AT*> > > result;\r
+    for (unsigned i = 0; i < paths.size(); i++)\r
+      result.push_back(deconstify_arcs(paths[i]));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector digraph<NT,AT>::constify_nodes(const TYPENAME digraph<NT,AT>::node_vector& nodes) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    for (unsigned i = 0; i < nodes.size(); i++)\r
+    {\r
+      nodes[i].assert_valid(this);\r
+      result.push_back(nodes[i].constify());\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector digraph<NT,AT>::deconstify_nodes(const TYPENAME digraph<NT,AT>::const_node_vector& nodes) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_iterator<NT,AT,NT&,NT*> > result;\r
+    for (unsigned i = 0; i < nodes.size(); i++)\r
+    {\r
+      nodes[i].assert_valid(this);\r
+      result.push_back(nodes[i].deconstify());\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::npos(void)\r
+  {\r
+    return(unsigned)-1;\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Constructors etc.\r
+\r
+  template<typename NT, typename AT>\r
+  digraph<NT,AT>::digraph(void) :\r
+    m_nodes_begin(0), m_nodes_end(0), m_arcs_begin(0), m_arcs_end(0)\r
+  {\r
+    // node and arc lists are circular double-linked lists\r
+    // they start out empty (no dummy end node)\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  digraph<NT,AT>::~digraph(void)\r
+  {\r
+    clear();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  digraph<NT,AT>::digraph(const digraph<NT,AT>& r) :\r
+    m_nodes_begin(0), m_nodes_end(0), m_arcs_begin(0), m_arcs_end(0)\r
+  {\r
+    *this = r;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  digraph<NT,AT>& digraph<NT,AT>::operator=(const digraph<NT,AT>& r)\r
+  {\r
+    // make it self-copy safe i.e. a=a; is a valid instruction\r
+    if (this == &r) return *this;\r
+    clear();\r
+    // first phase is to copy the nodes, creating a map of cross references from the old nodes to their new equivalents\r
+    std::map<digraph_iterator<NT,AT,const NT&,const NT*>, digraph_iterator<NT,AT,NT&,NT*> > xref;\r
+    for (digraph_iterator<NT,AT,const NT&,const NT*> n = r.begin(); n != r.end(); n++)\r
+      xref[n] = insert(*n);\r
+    // second phase is to copy the arcs, using the map to convert the old to and from nodes to the new nodes\r
+    for (digraph_arc_iterator<NT,AT, const AT&,const AT*> a = r.arc_begin(); a != r.arc_end(); a++)\r
+      arc_insert(xref[r.arc_from(a)],xref[r.arc_to(a)],*a);\r
+    return *this;\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Basic Node functions\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::empty(void) const\r
+  {\r
+    return m_nodes_begin == 0;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::size(void) const\r
+  {\r
+    unsigned count = 0;\r
+    for (digraph_iterator<NT,AT,const NT&,const NT*> i = begin(); i != end(); i++)\r
+      count++;\r
+    return count;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::insert(const NT& node_data)\r
+  {\r
+    digraph_node<NT,AT>* new_node = new digraph_node<NT,AT>(this,node_data);\r
+    if (!m_nodes_end)\r
+    {\r
+      // insert into an empty list\r
+      m_nodes_begin = new_node;\r
+      m_nodes_end = new_node;\r
+    }\r
+    else\r
+    {\r
+      // insert at the end of the list\r
+      new_node->m_prev = m_nodes_end;\r
+      m_nodes_end->m_next = new_node;\r
+      m_nodes_end = new_node;\r
+    }\r
+    return digraph_iterator<NT,AT,NT&,NT*>(new_node);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::erase(TYPENAME digraph<NT,AT>::iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    // remove all arcs connected to this node first\r
+    // use arc_erase rather than arcs.erase because that tidies up the node at the other end of the arc too\r
+    for (unsigned i = fanin(iter); i--; )\r
+      arc_erase(input(iter,i));\r
+    for (unsigned j = fanout(iter); j--; )\r
+      arc_erase(output(iter,j));\r
+    // now unlink the node from the list and delete it\r
+    if (iter.node()->m_next)\r
+      iter.node()->m_next->m_prev = iter.node()->m_prev;\r
+    if (iter.node()->m_prev)\r
+      iter.node()->m_prev->m_next = iter.node()->m_next;\r
+    digraph_node<NT,AT>* next = iter.node()->m_next;\r
+    delete iter.node();\r
+    // return the next node in the list\r
+    if (next)\r
+      return digraph_iterator<NT,AT,NT&,NT*>(next);\r
+    else\r
+      return digraph_iterator<NT,AT,NT&,NT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::clear(void)\r
+  {\r
+    // clearing the nodes also clears the arcs\r
+    for (digraph_iterator<NT,AT,NT&,NT*> i = begin(); i != end(); )\r
+      i = erase(i);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_iterator digraph<NT,AT>::begin(void) const\r
+  {\r
+    if (m_nodes_begin)\r
+      return digraph_iterator<NT,AT,const NT&,const NT*>(m_nodes_begin);\r
+    else\r
+      return digraph_iterator<NT,AT,const NT&,const NT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::begin(void)\r
+  {\r
+    if (m_nodes_begin)\r
+      return digraph_iterator<NT,AT,NT&,NT*>(m_nodes_begin);\r
+    else\r
+      return digraph_iterator<NT,AT,NT&,NT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_iterator digraph<NT,AT>::end(void) const\r
+  {\r
+    return digraph_iterator<NT,AT,const NT&,const NT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::end(void)\r
+  {\r
+    return digraph_iterator<NT,AT,NT&,NT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::fanin(TYPENAME digraph<NT,AT>::const_iterator iter) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return iter.node()->m_inputs.size();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::fanin(TYPENAME digraph<NT,AT>::iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return iter.node()->m_inputs.size();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_iterator digraph<NT,AT>::input(TYPENAME digraph<NT,AT>::const_iterator iter, unsigned i) const\r
+    throw(wrong_object,null_dereference,end_dereference,std::out_of_range)\r
+  {\r
+    iter.assert_valid(this);\r
+    if (i >= iter.node()->m_inputs.size()) throw std::out_of_range("digraph::input");\r
+    return digraph_arc_iterator<NT,AT, const AT&,const AT*>(iter.node()->m_inputs[i]);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::input(TYPENAME digraph<NT,AT>::iterator iter, unsigned i)\r
+    throw(wrong_object,null_dereference,end_dereference,std::out_of_range)\r
+  {\r
+    iter.assert_valid(this);\r
+    if (i >= iter.node()->m_inputs.size()) throw std::out_of_range("digraph::input");\r
+    return digraph_arc_iterator<NT,AT,AT&,AT*>(iter.node()->m_inputs[i]);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::fanout(TYPENAME digraph<NT,AT>::const_iterator iter) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return iter.node()->m_outputs.size();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::fanout(TYPENAME digraph<NT,AT>::iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return iter.node()->m_outputs.size();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_iterator digraph<NT,AT>::output(TYPENAME digraph<NT,AT>::const_iterator iter, unsigned i) const\r
+    throw(wrong_object,null_dereference,end_dereference,std::out_of_range)\r
+  {\r
+    iter.assert_valid(this);\r
+    if (i >= iter.node()->m_outputs.size()) throw std::out_of_range("digraph::output");\r
+    return digraph_arc_iterator<NT,AT, const AT&,const AT*>(iter.node()->m_outputs[i]);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::output(TYPENAME digraph<NT,AT>::iterator iter, unsigned i)\r
+    throw(wrong_object,null_dereference,end_dereference,std::out_of_range)\r
+  {\r
+    iter.assert_valid(this);\r
+    if (i >= iter.node()->m_outputs.size()) throw std::out_of_range("digraph::output");\r
+    return digraph_arc_iterator<NT,AT,AT&,AT*>(iter.node()->m_outputs[i]);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_vector digraph<NT,AT>::inputs(TYPENAME digraph<NT,AT>::const_iterator node) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    node.assert_valid(this);\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&, const AT*> > result;\r
+    for (unsigned i = 0; i < fanin(node); i++)\r
+      result.push_back(input(node,i));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_vector digraph<NT,AT>::inputs(TYPENAME digraph<NT,AT>::iterator node)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    node.assert_valid(this);\r
+    std::vector<digraph_arc_iterator<NT,AT,AT&,AT*> > result;\r
+    for (unsigned i = 0; i < fanin(node); i++)\r
+      result.push_back(input(node,i));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_vector digraph<NT,AT>::outputs(TYPENAME digraph<NT,AT>::const_iterator node) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    node.assert_valid(this);\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&, const AT*> > result;\r
+    for (unsigned i = 0; i < fanout(node); i++)\r
+      result.push_back(output(node,i));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_vector digraph<NT,AT>::outputs(TYPENAME digraph<NT,AT>::iterator node)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    node.assert_valid(this);\r
+    std::vector<digraph_arc_iterator<NT,AT,AT&,AT*> > result;\r
+    for (unsigned i = 0; i < fanout(node); i++)\r
+      result.push_back(output(node,i));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::output_offset(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                         TYPENAME digraph<NT,AT>::const_arc_iterator arc) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    arc.assert_valid(this);\r
+    for (unsigned i = 0; i < fanout(from); i++)\r
+    {\r
+      if (output(from,i) == arc)\r
+        return i;\r
+    }\r
+    return digraph<NT,AT>::npos();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::output_offset(TYPENAME digraph<NT,AT>::iterator from,\r
+                                         TYPENAME digraph<NT,AT>::arc_iterator arc)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    arc.assert_valid(this);\r
+    for (unsigned i = 0; i < fanout(from); i++)\r
+    {\r
+      if (output(from,i) == arc)\r
+        return i;\r
+    }\r
+    return digraph<NT,AT>::npos();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::input_offset(TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                        TYPENAME digraph<NT,AT>::const_arc_iterator arc) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    to.assert_valid(this);\r
+    arc.assert_valid(this);\r
+    for (unsigned i = 0; i < fanin(to); i++)\r
+    {\r
+      if (input(to,i) == arc)\r
+        return i;\r
+    }\r
+    return digraph<NT,AT>::npos();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::input_offset(TYPENAME digraph<NT,AT>::iterator to,\r
+                                        TYPENAME digraph<NT,AT>::arc_iterator arc)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    to.assert_valid(this);\r
+    arc.assert_valid(this);\r
+    for (unsigned i = 0; i < fanin(to); i++)\r
+    {\r
+      if (input(to,i) == arc)\r
+        return i;\r
+    }\r
+    return digraph<NT,AT>::npos();\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Basic Arc functions\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::arc_empty(void) const\r
+  {\r
+    return m_arcs_end == 0;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  unsigned digraph<NT,AT>::arc_size(void) const\r
+  {\r
+    unsigned count = 0;\r
+    for (digraph_arc_iterator<NT,AT, const AT&,const AT*> i = arc_begin(); i != arc_end(); i++)\r
+      count++;\r
+    return count;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::arc_insert(TYPENAME digraph<NT,AT>::iterator from,\r
+                                                                   TYPENAME digraph<NT,AT>::iterator to,\r
+                                                                   const AT& arc_data)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    to.assert_valid(this);\r
+    // create the new arc and link it in to the arc list\r
+    digraph_arc<NT,AT>* new_arc = new digraph_arc<NT,AT>(this, from.node(), to.node(), arc_data);\r
+    if (!m_arcs_end)\r
+    {\r
+      // insert into an empty list\r
+      m_arcs_begin = new_arc;\r
+      m_arcs_end = new_arc;\r
+    }\r
+    else\r
+    {\r
+      // insert at the end of the list\r
+      new_arc->m_prev = m_arcs_end;\r
+      m_arcs_end->m_next = new_arc;\r
+      m_arcs_end = new_arc;\r
+    }\r
+    // add this arc to the inputs and outputs of the end nodes\r
+    from.node()->m_outputs.push_back(new_arc);\r
+    to.node()->m_inputs.push_back(new_arc);\r
+    return digraph_arc_iterator<NT,AT,AT&,AT*>(new_arc);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::arc_erase(TYPENAME digraph<NT,AT>::arc_iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    // first remove this arc's pointers from the from/to nodes\r
+    for (TYPENAME std::vector<digraph_arc<NT,AT>*>::iterator i = iter.node()->m_to->m_inputs.begin(); i != iter.node()->m_to->m_inputs.end(); )\r
+    {\r
+      if (*i == iter.node())\r
+        i = iter.node()->m_to->m_inputs.erase(i);\r
+      else\r
+        i++;\r
+    }\r
+    for (TYPENAME std::vector<digraph_arc<NT,AT>*>::iterator o = iter.node()->m_from->m_outputs.begin(); o != iter.node()->m_from->m_outputs.end(); )\r
+    {\r
+      if (*o == iter.node())\r
+        o = iter.node()->m_from->m_outputs.erase(o);\r
+      else\r
+        o++;\r
+    }\r
+    // now unlink the arc from the list and delete it\r
+    if (iter.node()->m_next)\r
+      iter.node()->m_next->m_prev = iter.node()->m_prev;\r
+    if (iter.node()->m_prev)\r
+      iter.node()->m_prev->m_next = iter.node()->m_next;\r
+    digraph_arc<NT,AT>* next = iter.node()->m_next;\r
+    delete iter.node();\r
+    if (next)\r
+      return digraph_arc_iterator<NT,AT,AT&,AT*>(next);\r
+    else\r
+      return digraph_arc_iterator<NT,AT,AT&,AT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::arc_clear(void)\r
+  {\r
+    for (digraph_arc_iterator<NT,AT,AT&,AT*> a = arc_begin(); a != arc_end(); )\r
+      a = arc_erase(a);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_iterator digraph<NT,AT>::arc_begin(void) const\r
+  {\r
+    if (m_arcs_begin)\r
+      return digraph_arc_iterator<NT,AT, const AT&,const AT*>(m_arcs_begin);\r
+    else\r
+      return digraph_arc_iterator<NT,AT, const AT&,const AT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::arc_begin(void)\r
+  {\r
+    if (m_arcs_begin)\r
+      return digraph_arc_iterator<NT,AT,AT&,AT*>(m_arcs_begin);\r
+    else\r
+      return digraph_arc_iterator<NT,AT,AT&,AT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_iterator digraph<NT,AT>::arc_end(void) const\r
+  {\r
+    return digraph_arc_iterator<NT,AT, const AT&,const AT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::arc_end(void)\r
+  {\r
+    return digraph_arc_iterator<NT,AT,AT&,AT*>(this);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_iterator digraph<NT,AT>::arc_from(TYPENAME digraph<NT,AT>::const_arc_iterator iter) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return digraph_iterator<NT,AT,const NT&,const NT*>(iter.node()->m_from);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::arc_from(TYPENAME digraph<NT,AT>::arc_iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return digraph_iterator<NT,AT,NT&,NT*>(iter.node()->m_from);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_iterator digraph<NT,AT>::arc_to(TYPENAME digraph<NT,AT>::const_arc_iterator iter) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return digraph_iterator<NT,AT,const NT&,const NT*>(iter.node()->m_to);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::iterator digraph<NT,AT>::arc_to(TYPENAME digraph<NT,AT>::arc_iterator iter)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    iter.assert_valid(this);\r
+    return digraph_iterator<NT,AT,NT&,NT*>(iter.node()->m_to);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::arc_move(TYPENAME digraph<NT,AT>::arc_iterator arc,\r
+                                TYPENAME digraph<NT,AT>::iterator from,\r
+                                TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    arc_move_to(arc,to);\r
+    arc_move_from(arc,from);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::arc_move_from(TYPENAME digraph<NT,AT>::arc_iterator arc,\r
+                                     TYPENAME digraph<NT,AT>::iterator from)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    arc.assert_valid(this);\r
+    from.assert_valid(this);\r
+    for (TYPENAME std::vector<digraph_arc<NT,AT>*>::iterator o = arc.node()->m_from->m_outputs.begin(); o != arc.node()->m_from->m_outputs.end(); )\r
+    {\r
+      if (*o == arc.node())\r
+        o = arc.node()->m_from->m_outputs.erase(o);\r
+      else\r
+        o++;\r
+    }\r
+    from.node()->m_outputs.push_back(arc.node());\r
+    arc.node()->m_from = from.node();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::arc_move_to(TYPENAME digraph<NT,AT>::arc_iterator arc,\r
+                                   TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    arc.assert_valid(this);\r
+    to.assert_valid(this);\r
+    for (TYPENAME std::vector<digraph_arc<NT,AT>*>::iterator i = arc.node()->m_to->m_inputs.begin(); i != arc.node()->m_to->m_inputs.end(); )\r
+    {\r
+      if (*i == arc.node())\r
+        i = arc.node()->m_to->m_inputs.erase(i);\r
+      else\r
+        i++;\r
+    }\r
+    to.node()->m_inputs.push_back(arc.node());\r
+    arc.node()->m_to = to.node();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::arc_flip(TYPENAME digraph<NT,AT>::arc_iterator arc)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    arc_move(arc,arc_to(arc),arc_from(arc));\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Adjacency Algorithms\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::adjacent(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                TYPENAME digraph<NT,AT>::const_iterator to) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return adjacent_arc(from,to) != arc_end();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::adjacent(TYPENAME digraph<NT,AT>::iterator from,\r
+                                TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return adjacent_arc(from,to) != arc_end();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_iterator digraph<NT,AT>::adjacent_arc(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                                                           TYPENAME digraph<NT,AT>::const_iterator to) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    to.assert_valid(this);\r
+    for (unsigned arc = 0; arc < fanout(from); arc++)\r
+    {\r
+      if (arc_to(output(from, arc)) == to)\r
+        return output(from,arc);\r
+    }\r
+    return arc_end();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_iterator digraph<NT,AT>::adjacent_arc(TYPENAME digraph<NT,AT>::iterator from,\r
+                                                                     TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return adjacent_arc(from.constify(), to.constify()).deconstify();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_vector digraph<NT,AT>::adjacent_arcs(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                                                          TYPENAME digraph<NT,AT>::const_iterator to) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    to.assert_valid(this);\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > result;\r
+    for (unsigned arc = 0; arc < fanout(from); arc++)\r
+    {\r
+      if (arc_to(output(from, arc)) == to)\r
+        result.push_back(output(from,arc));\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_vector digraph<NT,AT>::adjacent_arcs(TYPENAME digraph<NT,AT>::iterator from,\r
+                                                                    TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_arcs(adjacent_arcs(from.constify(), to.constify()));\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector digraph<NT,AT>::input_adjacencies(TYPENAME digraph<NT,AT>::const_iterator to) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    for (unsigned arc = 0; arc < fanin(to); arc++)\r
+    {\r
+      digraph_iterator<NT,AT,const NT&,const NT*> from = arc_from(input(to, arc));\r
+      if (std::find(result.begin(), result.end(), from) == result.end())\r
+        result.push_back(from);\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector digraph<NT,AT>::input_adjacencies(TYPENAME digraph<NT,AT>::iterator to)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_nodes(input_adjacencies(to.constify()));\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector digraph<NT,AT>::output_adjacencies(TYPENAME digraph<NT,AT>::const_iterator from) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    for (unsigned arc = 0; arc < fanout(from); arc++)\r
+    {\r
+      digraph_iterator<NT,AT,const NT&,const NT*> to = arc_to(output(from, arc));\r
+      if (find(result.begin(), result.end(), to) == result.end())\r
+        result.push_back(to);\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector digraph<NT,AT>::output_adjacencies(TYPENAME digraph<NT,AT>::iterator from)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_nodes(output_adjacencies(from.constify()));\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Topographical Sort Algorithms\r
+\r
+  template<typename NT, typename AT>\r
+  std::pair<TYPENAME digraph<NT,AT>::const_node_vector, TYPENAME digraph<NT,AT>::const_arc_vector>\r
+  digraph<NT,AT>::sort(TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+  {\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > errors;\r
+    // build a map containing the number of fanins to each node that must be visited before this one\r
+    std::map<digraph_iterator<NT,AT,const NT&,const NT*>,unsigned> fanin_map;\r
+    for (digraph_iterator<NT,AT,const NT&,const NT*> n = begin(); n != end(); n++)\r
+    {\r
+      unsigned predecessors = 0;\r
+      // only count predecessors connected by selected arcs\r
+      for (unsigned f = 0; f < fanin(n); f++)\r
+      {\r
+        digraph_arc_iterator<NT,AT, const AT&,const AT*> input_arc = input(n,f);\r
+        digraph_iterator<NT,AT,const NT&,const NT*> predecessor = arc_from(input_arc);\r
+        if (!select || select(*this,input_arc))\r
+          predecessors++;\r
+      }\r
+      if (predecessors == 0)\r
+      {\r
+        result.push_back(n);\r
+      }\r
+      else\r
+      {\r
+        fanin_map[n] = predecessors;\r
+      }\r
+    }\r
+    // main algorithm applies the topographical sort repeatedly. For a DAG, it\r
+    // will complete first time. However, with backward arcs, the first\r
+    // iteration will fail. The algorithm then tries breaking random arcs to try\r
+    // to get an ordering.\r
+    for(unsigned i = 0; !fanin_map.empty(); )\r
+    {\r
+      // now visit each node in traversal order, decrementing the fanin count of\r
+      // all successors. As each successor's fanin count goes to zero, it is\r
+      // appended to the result.\r
+      for (; i < result.size(); i++)\r
+      {\r
+        // Note: dereferencing gives us a node iterator\r
+        digraph_iterator<NT,AT,const NT&,const NT*> current = result[i];\r
+        for (unsigned f = 0; f < fanout(current); f++)\r
+        {\r
+          // only consider successors connected by selected arcs\r
+          digraph_arc_iterator<NT,AT, const AT&,const AT*> output_arc = output(current, f);\r
+          digraph_iterator<NT,AT,const NT&,const NT*> successor = arc_to(output_arc);\r
+          if (!select || select(*this,output_arc))\r
+          {\r
+            // don't consider arcs that have been eliminated to break a loop\r
+            if (fanin_map.find(successor) != fanin_map.end())\r
+            {\r
+              --fanin_map[successor];\r
+              if ((fanin_map[successor]) == 0)\r
+              {\r
+                result.push_back(successor);\r
+                fanin_map.erase(fanin_map.find(successor));\r
+              }\r
+            }\r
+          }\r
+        }\r
+      }\r
+      if (!fanin_map.empty())\r
+      {\r
+        // there must be backward arcs preventing completion\r
+        // try removing arcs from the sort to get a partial ordering containing all the nodes\r
+\r
+        // select an arc that is still relevant to the sort and break it\r
+        // first select a node that has non-zero fanin and its predecessor that has non-zero fanin\r
+        digraph_iterator<NT,AT,const NT&,const NT*> stuck_node = fanin_map.begin()->first;\r
+        for (unsigned f = 0; f < fanin(stuck_node); f++)\r
+        {\r
+          // now successively remove input arcs that are still part of the sort until the fanin reduces to zero\r
+          // first find a relevant arc - this must be a selected arc that has not yet been traversed by the first half of the algorithm\r
+          digraph_arc_iterator<NT,AT, const AT&,const AT*> input_arc = input(stuck_node, f);\r
+          if (!select || select(*this,input_arc))\r
+          {\r
+            digraph_iterator<NT,AT,const NT&,const NT*> predecessor = arc_from(input_arc);\r
+            if (fanin_map.find(predecessor) != fanin_map.end())\r
+            {\r
+              // found the right combination - remove this arc and then drop out of the fanin loop to restart the outer sort loop\r
+              errors.push_back(input_arc);\r
+              --fanin_map[stuck_node];\r
+              if ((fanin_map[stuck_node]) == 0)\r
+              {\r
+                result.push_back(stuck_node);\r
+                fanin_map.erase(fanin_map.find(stuck_node));\r
+                break;\r
+              }\r
+            }\r
+          }\r
+        }\r
+      }\r
+    }\r
+    return std::make_pair(result,errors);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  std::pair<TYPENAME digraph<NT,AT>::node_vector, TYPENAME digraph<NT,AT>::arc_vector>\r
+  digraph<NT,AT>::sort(TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+  {\r
+    std::pair<std::vector<digraph_iterator<NT,AT,const NT&,const NT*> >,\r
+              std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > const_result =\r
+      const_cast<const digraph<NT,AT>*>(this)->sort(select);\r
+\r
+    std::pair<std::vector<digraph_iterator<NT,AT,NT&,NT*> >,\r
+              std::vector<digraph_arc_iterator<NT,AT,AT&,AT*> > > result =\r
+      std::make_pair(deconstify_nodes(const_result.first),deconstify_arcs(const_result.second));\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector digraph<NT,AT>::dag_sort(TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+  {\r
+    std::pair<std::vector<digraph_iterator<NT,AT,const NT&,const NT*> >,\r
+              std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > result = sort(select);\r
+    if (result.second.empty()) return result.first;\r
+    return std::vector<digraph_iterator<NT,AT,const NT&,const NT*> >();\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector digraph<NT,AT>::dag_sort(TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+  {\r
+    return deconstify_nodes(const_cast<const digraph<NT,AT>*>(this)->dag_sort(select));\r
+  }\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Path Algorithms\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::path_exists_r(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                     TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                     TYPENAME digraph<NT,AT>::const_iterator_set& visited,\r
+                                     TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // Recursive part of the digraph::path_exists function. This is based on a\r
+    // depth first search algorithm and stops the moment it finds a path\r
+    // regardless of its length. Simply traverse every output and recurse on that\r
+    // node until we find the to node or run out of things to recurse on. However,\r
+    // to avoid infinite recursion due to cycles in the graph, I need to maintain\r
+    // a set of visited nodes. The visited set is updated when a candidate is\r
+    // found but tested before the recursion on the candidate so that the number of\r
+    // function calls is minimised.\r
+    for (unsigned i = 0; i < fanout(from); i++)\r
+    {\r
+      digraph_arc_iterator<NT,AT, const AT&,const AT*> arc = output(from,i);\r
+      if (!select || select(*this, arc))\r
+      {\r
+        digraph_iterator<NT,AT,const NT&,const NT*> node = arc_to(arc);\r
+        // if the node is the target, return immediately\r
+        if (node == to) return true;\r
+        // update the visited set and give up if the insert fails, which indicates that the node has already been visited\r
+        if (!(visited.insert(node).second)) return false;\r
+        // now recurse - a path exists from from to to if a path exists from an adjacent node to to\r
+        if (path_exists_r(node,to,visited,select)) return true;\r
+      }\r
+    }\r
+    return false;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::path_exists(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                   TYPENAME digraph<NT,AT>::const_iterator to, \r
+                                   TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // set up the recursion with its initial visited set and then recurse\r
+    std::set<digraph_iterator<NT,AT,const NT&,const NT*> > visited;\r
+    visited.insert(from);\r
+    return path_exists_r(from, to, visited, select);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  bool digraph<NT,AT>::path_exists(TYPENAME digraph<NT,AT>::iterator from,\r
+                                   TYPENAME digraph<NT,AT>::iterator to,\r
+                                   TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return path_exists(from.constify(), to.constify(), select);\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::all_paths_r(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                   TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                   TYPENAME digraph<NT,AT>::const_arc_vector& so_far,\r
+                                   TYPENAME digraph<NT,AT>::const_path_vector& result,\r
+                                   TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // This is the recursive part of the all_paths function. The field so_far\r
+    // contains the path so far so that when 'to' is reached, the path is\r
+    // complete. It serves the same purpose as the visited set in the path_exists\r
+    // function except that it also preserves the path order. It also serves the\r
+    // purpose of detecting cycles and thus stopping infinite recursion. Every\r
+    // time the recursion reaches the to node, a copy of so_far is appended to the\r
+    // path set.\r
+    for (unsigned i = 0; i < fanout(from); i++)\r
+    {\r
+      digraph_arc_iterator<NT,AT, const AT&,const AT*> candidate = output(from,i);\r
+      // assert_valid that the arc is selected and then assert_valid that the candidate has not\r
+      // been visited on this path and only allow further recursion if it hasn't\r
+      if ((!select || select(*this, candidate)) && std::find(so_far.begin(), so_far.end(), candidate) == so_far.end())\r
+      {\r
+        // extend the path tracing the route to this arc\r
+        so_far.push_back(candidate);\r
+        // if the candidate arc points to the target, update the result set and prevent further recursion, otherwise recurse\r
+        if (arc_to(candidate) == to)\r
+          result.push_back(so_far);\r
+        else\r
+          all_paths_r(arc_to(candidate),to,so_far,result,select);\r
+        so_far.pop_back();\r
+      }\r
+    }\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_path_vector \r
+  digraph<NT,AT>::all_paths(TYPENAME digraph<NT,AT>::const_iterator from, \r
+                            TYPENAME digraph<NT,AT>::const_iterator to,\r
+                            TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // set up the recursion with empty data fields and then recurse\r
+    std::vector<std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > result;\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > so_far;\r
+    all_paths_r(from, to, so_far, result, select);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::path_vector\r
+  digraph<NT,AT>::all_paths(TYPENAME digraph<NT,AT>::iterator from, \r
+                            TYPENAME digraph<NT,AT>::iterator to,\r
+                            TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_paths(all_paths(from.constify(), to.constify(), select));\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::reachable_nodes_r(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                         TYPENAME digraph<NT,AT>::const_iterator_set& visited,\r
+                                         TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // The recursive part of the reachable_nodes function.\r
+    // This is a depth-first traversal again but this time it carries on to find all the reachable nodes\r
+    // Just keep recursing on all the adjacent nodes of each node, skipping already visited nodes to avoid cycles\r
+    for (unsigned i = 0; i < fanout(from); i++)\r
+    {\r
+      digraph_arc_iterator<NT,AT, const AT&,const AT*> arc = output(from,i);\r
+      if (!select || select(*this,arc))\r
+      {\r
+        digraph_iterator<NT,AT,const NT&,const NT*> candidate = arc_to(arc);\r
+        if (visited.insert(candidate).second)\r
+          reachable_nodes_r(candidate,visited,select);\r
+      }\r
+    }\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector\r
+  digraph<NT,AT>::reachable_nodes(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                  TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // seed the recursion, marking the starting node as already visited\r
+    std::set<digraph_iterator<NT,AT,const NT&,const NT*> > visited;\r
+    visited.insert(from);\r
+    reachable_nodes_r(from, visited, select);\r
+    // convert the visited set into the required output form\r
+    // exclude the starting node\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    for (TYPENAME std::set<digraph_iterator<NT,AT,const NT&,const NT*> >::iterator i = visited.begin(); i != visited.end(); i++)\r
+      if (*i != from)\r
+        result.push_back(*i);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector\r
+  digraph<NT,AT>::reachable_nodes(TYPENAME digraph<NT,AT>::iterator from,\r
+                                  TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_nodes(reachable_nodes(from.constify(), select));\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  void digraph<NT,AT>::reaching_nodes_r(TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                        TYPENAME digraph<NT,AT>::const_iterator_set& visited,\r
+                                        TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // The recursive part of the reaching_nodes function.\r
+    // Just like the reachable_nodes_r function but it goes backwards\r
+    for (unsigned i = 0; i < fanin(to); i++)\r
+    {\r
+      digraph_arc_iterator<NT,AT, const AT&,const AT*> arc = input(to,i);\r
+      if (!select || select(*this,arc))\r
+      {\r
+        digraph_iterator<NT,AT,const NT&,const NT*> candidate = arc_from(input(to,i));\r
+        if (visited.insert(candidate).second)\r
+          reaching_nodes_r(candidate,visited,select);\r
+      }\r
+    }\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_node_vector\r
+  digraph<NT,AT>::reaching_nodes(TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                 TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    // seed the recursion, marking the starting node as already visited\r
+    std::set<digraph_iterator<NT,AT,const NT&,const NT*> > visited;\r
+    visited.insert(to);\r
+    reaching_nodes_r(to,visited,select);\r
+    // convert the visited set into the required output form\r
+    // exclude the end node\r
+    std::vector<digraph_iterator<NT,AT,const NT&,const NT*> > result;\r
+    for (TYPENAME std::set<digraph_iterator<NT,AT,const NT&,const NT*> >::iterator i = visited.begin(); i != visited.end(); i++)\r
+      if (*i != to)\r
+        result.push_back(*i);\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::node_vector\r
+  digraph<NT,AT>::reaching_nodes(TYPENAME digraph<NT,AT>::iterator to,\r
+                                 TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_nodes(reaching_nodes(to.constify(),select));\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+  // Shortest Path Algorithms\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_arc_vector\r
+  digraph<NT,AT>::shortest_path(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                TYPENAME digraph<NT,AT>::const_iterator to,\r
+                                TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    std::vector<std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > paths = all_paths(from,to,select);\r
+    std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > shortest;\r
+    for (TYPENAME std::vector<std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > >::iterator i = paths.begin(); i != paths.end(); i++)\r
+      if (shortest.empty() || i->size() < shortest.size())\r
+        shortest = *i;\r
+    return shortest;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::arc_vector\r
+  digraph<NT,AT>::shortest_path(TYPENAME digraph<NT,AT>::iterator from, \r
+                                TYPENAME digraph<NT,AT>::iterator to,\r
+                                TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_arcs(shortest_path(from.constify(),to.constify(),select));\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::const_path_vector\r
+  digraph<NT,AT>::shortest_paths(TYPENAME digraph<NT,AT>::const_iterator from,\r
+                                 TYPENAME digraph<NT,AT>::arc_select_fn select) const\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    from.assert_valid(this);\r
+    // This is an unweighted shortest path algorithm based on the algorithm from\r
+    // Weiss's book. This is essentially a breadth-first traversal or graph\r
+    // colouring algorithm. It is an iterative algorithm, so no recursion here! It\r
+    // works by creating a node queue initialised with the starting node. It then\r
+    // consumes the queue from front to back. For each node, it finds the\r
+    // successors and appends them to the queue. If a node is already 'known' it\r
+    // is not added - this avoids cycles. Thus the queue insert ordering\r
+    // represents the breadth-first ordering. On the way it creates a map of\r
+    // visited nodes. This is a map not a set because it also stores the arc that\r
+    // nominated this node as a shortest path. The full path can then be recreated\r
+    // from the map by just walking back through the predecessors. The depth (or\r
+    // colour) can be determined by the path length.\r
+    std::vector<std::vector<digraph_arc_iterator<NT,AT,const AT&,const AT*> > > result;\r
+    // initialise the iteration by creating a queue and adding the start node\r
+    std::deque<digraph_iterator<NT,AT,const NT&,const NT*> > nodes;\r
+    nodes.push_back(from);\r
+    // Create a map to store the set of known nodes mapped to their predecessor\r
+    // arcs. Initialise it with the current node, which has no predecessor. Note\r
+    // that the algorithm uses the feature of digraph iterators that they can be\r
+    // null iterators and that all null iterators are equal.\r
+    typedef std::map<digraph_iterator<NT,AT,const NT&,const NT*>,\r
+                     digraph_arc_iterator<NT,AT,const AT&,const AT*> > known_map;\r
+    known_map known;\r
+    known.insert(std::make_pair(from,digraph_arc_iterator<NT,AT, const AT&,const AT*>()));\r
+    // now the iterative part of the algorithm\r
+    while(!nodes.empty())\r
+    {\r
+      // pop the queue to get the next node to process - unfortunately the STL\r
+      // deque::pop does not return the popped value\r
+      digraph_iterator<NT,AT,const NT&,const NT*> current = nodes.front();\r
+      nodes.pop_front();\r
+      // now visit all the successors\r
+      for (unsigned i = 0; i < fanout(current); i++)\r
+      {\r
+        digraph_arc_iterator<NT,AT, const AT&,const AT*> next_arc = output(current,i);\r
+        // assert_valid whether the successor arc is a selected arc and can be part of a path\r
+        if (!select || select(*this,next_arc))\r
+        {\r
+          digraph_iterator<NT,AT,const NT&,const NT*> next = arc_to(next_arc);\r
+          // Discard any successors that are known because to be known already they\r
+          // must have another shorter path. Otherwise add the successor node to the\r
+          // queue to be visited later. To minimise the overhead of map lookup I use\r
+          // the usual trick of trying to insert the node and determining whether\r
+          // the node was known by the success or failure of the insertion - this is\r
+          // a Good STL Trick (TM).\r
+          if (known.insert(std::make_pair(next,next_arc)).second)\r
+            nodes.push_back(next);\r
+        }\r
+      }\r
+    }\r
+    // The map contains the results as an unordered set of nodes, mapped to their\r
+    // predecessor arcs and weight. This now needs to be converted into a set of\r
+    // paths. This is done by starting with a node from the map, finding its\r
+    // predecessor arc and therefore its predecessor node, looking that up in the\r
+    // map to find its predecessor and so on until the start node is reached (it\r
+    // has a null predecessor). Note that the known set includes the from node\r
+    // which does not generate a path.\r
+    for (TYPENAME known_map::iterator i = known.begin(); i != known.end(); i++)\r
+    {\r
+      if (i->first != from)\r
+      {\r
+        const_arc_vector this_path;\r
+        for (TYPENAME known_map::iterator node = i; \r
+             node->second.valid(); \r
+             node = known.find(arc_from(node->second)))\r
+          this_path.insert(this_path.begin(),node->second);\r
+        result.push_back(this_path);\r
+      }\r
+    }\r
+    return result;\r
+  }\r
+\r
+  template<typename NT, typename AT>\r
+  TYPENAME digraph<NT,AT>::path_vector\r
+  digraph<NT,AT>::shortest_paths(TYPENAME digraph<NT,AT>::iterator from,\r
+                                 TYPENAME digraph<NT,AT>::arc_select_fn select)\r
+    throw(wrong_object,null_dereference,end_dereference)\r
+  {\r
+    return deconstify_paths(shortest_paths(from.constify(),select));\r
+  }\r
+\r
+  ////////////////////////////////////////////////////////////////////////////////\r
+\r
+} // end namespace stlplus\r
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