COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/concepts/graph_components.h @ 967:c5990f454032

Last change on this file since 967:c5990f454032 was 963:761fe0846f49, checked in by Alpar Juttner <alpar@…>, 7 years ago

Fix clang compilation warnings and errors (#449)

File size: 48.5 KB
Line 
1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2009
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19///\ingroup graph_concepts
20///\file
21///\brief The concept of graph components.
22
23#ifndef LEMON_CONCEPTS_GRAPH_COMPONENTS_H
24#define LEMON_CONCEPTS_GRAPH_COMPONENTS_H
25
26#include <lemon/core.h>
27#include <lemon/concepts/maps.h>
28
29#include <lemon/bits/alteration_notifier.h>
30
31namespace lemon {
32  namespace concepts {
33
34    /// \brief Concept class for \c Node, \c Arc and \c Edge types.
35    ///
36    /// This class describes the concept of \c Node, \c Arc and \c Edge
37    /// subtypes of digraph and graph types.
38    ///
39    /// \note This class is a template class so that we can use it to
40    /// create graph skeleton classes. The reason for this is that \c Node
41    /// and \c Arc (or \c Edge) types should \e not derive from the same
42    /// base class. For \c Node you should instantiate it with character
43    /// \c 'n', for \c Arc with \c 'a' and for \c Edge with \c 'e'.
44#ifndef DOXYGEN
45    template <char sel = '0'>
46#endif
47    class GraphItem {
48    public:
49      /// \brief Default constructor.
50      ///
51      /// Default constructor.
52      /// \warning The default constructor is not required to set
53      /// the item to some well-defined value. So you should consider it
54      /// as uninitialized.
55      GraphItem() {}
56
57      /// \brief Copy constructor.
58      ///
59      /// Copy constructor.
60      GraphItem(const GraphItem &) {}
61
62      /// \brief Constructor for conversion from \c INVALID.
63      ///
64      /// Constructor for conversion from \c INVALID.
65      /// It initializes the item to be invalid.
66      /// \sa Invalid for more details.
67      GraphItem(Invalid) {}
68
69      /// \brief Assignment operator.
70      ///
71      /// Assignment operator for the item.
72      GraphItem& operator=(const GraphItem&) { return *this; }
73
74      /// \brief Assignment operator for INVALID.
75      ///
76      /// This operator makes the item invalid.
77      GraphItem& operator=(Invalid) { return *this; }
78
79      /// \brief Equality operator.
80      ///
81      /// Equality operator.
82      bool operator==(const GraphItem&) const { return false; }
83
84      /// \brief Inequality operator.
85      ///
86      /// Inequality operator.
87      bool operator!=(const GraphItem&) const { return false; }
88
89      /// \brief Ordering operator.
90      ///
91      /// This operator defines an ordering of the items.
92      /// It makes possible to use graph item types as key types in
93      /// associative containers (e.g. \c std::map).
94      ///
95      /// \note This operator only have to define some strict ordering of
96      /// the items; this order has nothing to do with the iteration
97      /// ordering of the items.
98      bool operator<(const GraphItem&) const { return false; }
99
100      template<typename _GraphItem>
101      struct Constraints {
102        void constraints() {
103          _GraphItem i1;
104          i1=INVALID;
105          _GraphItem i2 = i1;
106          _GraphItem i3 = INVALID;
107
108          i1 = i2 = i3;
109
110          bool b;
111          b = (ia == ib) && (ia != ib);
112          b = (ia == INVALID) && (ib != INVALID);
113          b = (ia < ib);
114        }
115
116        const _GraphItem &ia;
117        const _GraphItem &ib;
118        Constraints() {}
119      };
120    };
121
122    /// \brief Base skeleton class for directed graphs.
123    ///
124    /// This class describes the base interface of directed graph types.
125    /// All digraph %concepts have to conform to this class.
126    /// It just provides types for nodes and arcs and functions
127    /// to get the source and the target nodes of arcs.
128    class BaseDigraphComponent {
129    public:
130
131      typedef BaseDigraphComponent Digraph;
132
133      /// \brief Node class of the digraph.
134      ///
135      /// This class represents the nodes of the digraph.
136      typedef GraphItem<'n'> Node;
137
138      /// \brief Arc class of the digraph.
139      ///
140      /// This class represents the arcs of the digraph.
141      typedef GraphItem<'a'> Arc;
142
143      /// \brief Return the source node of an arc.
144      ///
145      /// This function returns the source node of an arc.
146      Node source(const Arc&) const { return INVALID; }
147
148      /// \brief Return the target node of an arc.
149      ///
150      /// This function returns the target node of an arc.
151      Node target(const Arc&) const { return INVALID; }
152
153      /// \brief Return the opposite node on the given arc.
154      ///
155      /// This function returns the opposite node on the given arc.
156      Node oppositeNode(const Node&, const Arc&) const {
157        return INVALID;
158      }
159
160      template <typename _Digraph>
161      struct Constraints {
162        typedef typename _Digraph::Node Node;
163        typedef typename _Digraph::Arc Arc;
164
165        void constraints() {
166          checkConcept<GraphItem<'n'>, Node>();
167          checkConcept<GraphItem<'a'>, Arc>();
168          {
169            Node n;
170            Arc e(INVALID);
171            n = digraph.source(e);
172            n = digraph.target(e);
173            n = digraph.oppositeNode(n, e);
174          }
175        }
176
177        const _Digraph& digraph;
178        Constraints() {}
179      };
180    };
181
182    /// \brief Base skeleton class for undirected graphs.
183    ///
184    /// This class describes the base interface of undirected graph types.
185    /// All graph %concepts have to conform to this class.
186    /// It extends the interface of \ref BaseDigraphComponent with an
187    /// \c Edge type and functions to get the end nodes of edges,
188    /// to convert from arcs to edges and to get both direction of edges.
189    class BaseGraphComponent : public BaseDigraphComponent {
190    public:
191
192      typedef BaseGraphComponent Graph;
193
194      typedef BaseDigraphComponent::Node Node;
195      typedef BaseDigraphComponent::Arc Arc;
196
197      /// \brief Undirected edge class of the graph.
198      ///
199      /// This class represents the undirected edges of the graph.
200      /// Undirected graphs can be used as directed graphs, each edge is
201      /// represented by two opposite directed arcs.
202      class Edge : public GraphItem<'e'> {
203        typedef GraphItem<'e'> Parent;
204
205      public:
206        /// \brief Default constructor.
207        ///
208        /// Default constructor.
209        /// \warning The default constructor is not required to set
210        /// the item to some well-defined value. So you should consider it
211        /// as uninitialized.
212        Edge() {}
213
214        /// \brief Copy constructor.
215        ///
216        /// Copy constructor.
217        Edge(const Edge &) : Parent() {}
218
219        /// \brief Constructor for conversion from \c INVALID.
220        ///
221        /// Constructor for conversion from \c INVALID.
222        /// It initializes the item to be invalid.
223        /// \sa Invalid for more details.
224        Edge(Invalid) {}
225
226        /// \brief Constructor for conversion from an arc.
227        ///
228        /// Constructor for conversion from an arc.
229        /// Besides the core graph item functionality each arc should
230        /// be convertible to the represented edge.
231        Edge(const Arc&) {}
232     };
233
234      /// \brief Return one end node of an edge.
235      ///
236      /// This function returns one end node of an edge.
237      Node u(const Edge&) const { return INVALID; }
238
239      /// \brief Return the other end node of an edge.
240      ///
241      /// This function returns the other end node of an edge.
242      Node v(const Edge&) const { return INVALID; }
243
244      /// \brief Return a directed arc related to an edge.
245      ///
246      /// This function returns a directed arc from its direction and the
247      /// represented edge.
248      Arc direct(const Edge&, bool) const { return INVALID; }
249
250      /// \brief Return a directed arc related to an edge.
251      ///
252      /// This function returns a directed arc from its source node and the
253      /// represented edge.
254      Arc direct(const Edge&, const Node&) const { return INVALID; }
255
256      /// \brief Return the direction of the arc.
257      ///
258      /// Returns the direction of the arc. Each arc represents an
259      /// edge with a direction. It gives back the
260      /// direction.
261      bool direction(const Arc&) const { return true; }
262
263      /// \brief Return the opposite arc.
264      ///
265      /// This function returns the opposite arc, i.e. the arc representing
266      /// the same edge and has opposite direction.
267      Arc oppositeArc(const Arc&) const { return INVALID; }
268
269      template <typename _Graph>
270      struct Constraints {
271        typedef typename _Graph::Node Node;
272        typedef typename _Graph::Arc Arc;
273        typedef typename _Graph::Edge Edge;
274
275        void constraints() {
276          checkConcept<BaseDigraphComponent, _Graph>();
277          checkConcept<GraphItem<'e'>, Edge>();
278          {
279            Node n;
280            Edge ue(INVALID);
281            Arc e;
282            n = graph.u(ue);
283            n = graph.v(ue);
284            e = graph.direct(ue, true);
285            e = graph.direct(ue, false);
286            e = graph.direct(ue, n);
287            e = graph.oppositeArc(e);
288            ue = e;
289            bool d = graph.direction(e);
290            ignore_unused_variable_warning(d);
291          }
292        }
293
294        const _Graph& graph;
295      Constraints() {}
296      };
297
298    };
299
300    /// \brief Skeleton class for \e idable directed graphs.
301    ///
302    /// This class describes the interface of \e idable directed graphs.
303    /// It extends \ref BaseDigraphComponent with the core ID functions.
304    /// The ids of the items must be unique and immutable.
305    /// This concept is part of the Digraph concept.
306    template <typename BAS = BaseDigraphComponent>
307    class IDableDigraphComponent : public BAS {
308    public:
309
310      typedef BAS Base;
311      typedef typename Base::Node Node;
312      typedef typename Base::Arc Arc;
313
314      /// \brief Return a unique integer id for the given node.
315      ///
316      /// This function returns a unique integer id for the given node.
317      int id(const Node&) const { return -1; }
318
319      /// \brief Return the node by its unique id.
320      ///
321      /// This function returns the node by its unique id.
322      /// If the digraph does not contain a node with the given id,
323      /// then the result of the function is undefined.
324      Node nodeFromId(int) const { return INVALID; }
325
326      /// \brief Return a unique integer id for the given arc.
327      ///
328      /// This function returns a unique integer id for the given arc.
329      int id(const Arc&) const { return -1; }
330
331      /// \brief Return the arc by its unique id.
332      ///
333      /// This function returns the arc by its unique id.
334      /// If the digraph does not contain an arc with the given id,
335      /// then the result of the function is undefined.
336      Arc arcFromId(int) const { return INVALID; }
337
338      /// \brief Return an integer greater or equal to the maximum
339      /// node id.
340      ///
341      /// This function returns an integer greater or equal to the
342      /// maximum node id.
343      int maxNodeId() const { return -1; }
344
345      /// \brief Return an integer greater or equal to the maximum
346      /// arc id.
347      ///
348      /// This function returns an integer greater or equal to the
349      /// maximum arc id.
350      int maxArcId() const { return -1; }
351
352      template <typename _Digraph>
353      struct Constraints {
354
355        void constraints() {
356          checkConcept<Base, _Digraph >();
357          typename _Digraph::Node node;
358          node=INVALID;
359          int nid = digraph.id(node);
360          nid = digraph.id(node);
361          node = digraph.nodeFromId(nid);
362          typename _Digraph::Arc arc;
363          arc=INVALID;
364          int eid = digraph.id(arc);
365          eid = digraph.id(arc);
366          arc = digraph.arcFromId(eid);
367
368          nid = digraph.maxNodeId();
369          ignore_unused_variable_warning(nid);
370          eid = digraph.maxArcId();
371          ignore_unused_variable_warning(eid);
372        }
373
374        const _Digraph& digraph;
375        Constraints() {}
376      };
377    };
378
379    /// \brief Skeleton class for \e idable undirected graphs.
380    ///
381    /// This class describes the interface of \e idable undirected
382    /// graphs. It extends \ref IDableDigraphComponent with the core ID
383    /// functions of undirected graphs.
384    /// The ids of the items must be unique and immutable.
385    /// This concept is part of the Graph concept.
386    template <typename BAS = BaseGraphComponent>
387    class IDableGraphComponent : public IDableDigraphComponent<BAS> {
388    public:
389
390      typedef BAS Base;
391      typedef typename Base::Edge Edge;
392
393      using IDableDigraphComponent<Base>::id;
394
395      /// \brief Return a unique integer id for the given edge.
396      ///
397      /// This function returns a unique integer id for the given edge.
398      int id(const Edge&) const { return -1; }
399
400      /// \brief Return the edge by its unique id.
401      ///
402      /// This function returns the edge by its unique id.
403      /// If the graph does not contain an edge with the given id,
404      /// then the result of the function is undefined.
405      Edge edgeFromId(int) const { return INVALID; }
406
407      /// \brief Return an integer greater or equal to the maximum
408      /// edge id.
409      ///
410      /// This function returns an integer greater or equal to the
411      /// maximum edge id.
412      int maxEdgeId() const { return -1; }
413
414      template <typename _Graph>
415      struct Constraints {
416
417        void constraints() {
418          checkConcept<IDableDigraphComponent<Base>, _Graph >();
419          typename _Graph::Edge edge;
420          int ueid = graph.id(edge);
421          ueid = graph.id(edge);
422          edge = graph.edgeFromId(ueid);
423          ueid = graph.maxEdgeId();
424          ignore_unused_variable_warning(ueid);
425        }
426
427        const _Graph& graph;
428        Constraints() {}
429      };
430    };
431
432    /// \brief Concept class for \c NodeIt, \c ArcIt and \c EdgeIt types.
433    ///
434    /// This class describes the concept of \c NodeIt, \c ArcIt and
435    /// \c EdgeIt subtypes of digraph and graph types.
436    template <typename GR, typename Item>
437    class GraphItemIt : public Item {
438    public:
439      /// \brief Default constructor.
440      ///
441      /// Default constructor.
442      /// \warning The default constructor is not required to set
443      /// the iterator to some well-defined value. So you should consider it
444      /// as uninitialized.
445      GraphItemIt() {}
446
447      /// \brief Copy constructor.
448      ///
449      /// Copy constructor.
450      GraphItemIt(const GraphItemIt& it) : Item(it) {}
451
452      /// \brief Constructor that sets the iterator to the first item.
453      ///
454      /// Constructor that sets the iterator to the first item.
455      explicit GraphItemIt(const GR&) {}
456
457      /// \brief Constructor for conversion from \c INVALID.
458      ///
459      /// Constructor for conversion from \c INVALID.
460      /// It initializes the iterator to be invalid.
461      /// \sa Invalid for more details.
462      GraphItemIt(Invalid) {}
463
464      /// \brief Assignment operator.
465      ///
466      /// Assignment operator for the iterator.
467      GraphItemIt& operator=(const GraphItemIt&) { return *this; }
468
469      /// \brief Increment the iterator.
470      ///
471      /// This operator increments the iterator, i.e. assigns it to the
472      /// next item.
473      GraphItemIt& operator++() { return *this; }
474 
475      /// \brief Equality operator
476      ///
477      /// Equality operator.
478      /// Two iterators are equal if and only if they point to the
479      /// same object or both are invalid.
480      bool operator==(const GraphItemIt&) const { return true;}
481
482      /// \brief Inequality operator
483      ///
484      /// Inequality operator.
485      /// Two iterators are equal if and only if they point to the
486      /// same object or both are invalid.
487      bool operator!=(const GraphItemIt&) const { return true;}
488
489      template<typename _GraphItemIt>
490      struct Constraints {
491        void constraints() {
492          checkConcept<GraphItem<>, _GraphItemIt>();
493          _GraphItemIt it1(g);
494          _GraphItemIt it2;
495          _GraphItemIt it3 = it1;
496          _GraphItemIt it4 = INVALID;
497          ignore_unused_variable_warning(it3);
498          ignore_unused_variable_warning(it4);
499
500          it2 = ++it1;
501          ++it2 = it1;
502          ++(++it1);
503
504          Item bi = it1;
505          bi = it2;
506        }
507        const GR& g;
508        Constraints() {}
509      };
510    };
511
512    /// \brief Concept class for \c InArcIt, \c OutArcIt and
513    /// \c IncEdgeIt types.
514    ///
515    /// This class describes the concept of \c InArcIt, \c OutArcIt
516    /// and \c IncEdgeIt subtypes of digraph and graph types.
517    ///
518    /// \note Since these iterator classes do not inherit from the same
519    /// base class, there is an additional template parameter (selector)
520    /// \c sel. For \c InArcIt you should instantiate it with character
521    /// \c 'i', for \c OutArcIt with \c 'o' and for \c IncEdgeIt with \c 'e'.
522    template <typename GR,
523              typename Item = typename GR::Arc,
524              typename Base = typename GR::Node,
525              char sel = '0'>
526    class GraphIncIt : public Item {
527    public:
528      /// \brief Default constructor.
529      ///
530      /// Default constructor.
531      /// \warning The default constructor is not required to set
532      /// the iterator to some well-defined value. So you should consider it
533      /// as uninitialized.
534      GraphIncIt() {}
535
536      /// \brief Copy constructor.
537      ///
538      /// Copy constructor.
539      GraphIncIt(const GraphIncIt& it) : Item(it) {}
540
541      /// \brief Constructor that sets the iterator to the first
542      /// incoming or outgoing arc.
543      ///
544      /// Constructor that sets the iterator to the first arc
545      /// incoming to or outgoing from the given node.
546      explicit GraphIncIt(const GR&, const Base&) {}
547
548      /// \brief Constructor for conversion from \c INVALID.
549      ///
550      /// Constructor for conversion from \c INVALID.
551      /// It initializes the iterator to be invalid.
552      /// \sa Invalid for more details.
553      GraphIncIt(Invalid) {}
554
555      /// \brief Assignment operator.
556      ///
557      /// Assignment operator for the iterator.
558      GraphIncIt& operator=(const GraphIncIt&) { return *this; }
559
560      /// \brief Increment the iterator.
561      ///
562      /// This operator increments the iterator, i.e. assigns it to the
563      /// next arc incoming to or outgoing from the given node.
564      GraphIncIt& operator++() { return *this; }
565
566      /// \brief Equality operator
567      ///
568      /// Equality operator.
569      /// Two iterators are equal if and only if they point to the
570      /// same object or both are invalid.
571      bool operator==(const GraphIncIt&) const { return true;}
572
573      /// \brief Inequality operator
574      ///
575      /// Inequality operator.
576      /// Two iterators are equal if and only if they point to the
577      /// same object or both are invalid.
578      bool operator!=(const GraphIncIt&) const { return true;}
579
580      template <typename _GraphIncIt>
581      struct Constraints {
582        void constraints() {
583          checkConcept<GraphItem<sel>, _GraphIncIt>();
584          _GraphIncIt it1(graph, node);
585          _GraphIncIt it2;
586          _GraphIncIt it3 = it1;
587          _GraphIncIt it4 = INVALID;
588          ignore_unused_variable_warning(it3);
589          ignore_unused_variable_warning(it4);
590
591          it2 = ++it1;
592          ++it2 = it1;
593          ++(++it1);
594          Item e = it1;
595          e = it2;
596        }
597        const Base& node;
598        const GR& graph;
599        Constraints() {}
600      };
601    };
602
603    /// \brief Skeleton class for iterable directed graphs.
604    ///
605    /// This class describes the interface of iterable directed
606    /// graphs. It extends \ref BaseDigraphComponent with the core
607    /// iterable interface.
608    /// This concept is part of the Digraph concept.
609    template <typename BAS = BaseDigraphComponent>
610    class IterableDigraphComponent : public BAS {
611
612    public:
613
614      typedef BAS Base;
615      typedef typename Base::Node Node;
616      typedef typename Base::Arc Arc;
617
618      typedef IterableDigraphComponent Digraph;
619
620      /// \name Base Iteration
621      ///
622      /// This interface provides functions for iteration on digraph items.
623      ///
624      /// @{
625
626      /// \brief Return the first node.
627      ///
628      /// This function gives back the first node in the iteration order.
629      void first(Node&) const {}
630
631      /// \brief Return the next node.
632      ///
633      /// This function gives back the next node in the iteration order.
634      void next(Node&) const {}
635
636      /// \brief Return the first arc.
637      ///
638      /// This function gives back the first arc in the iteration order.
639      void first(Arc&) const {}
640
641      /// \brief Return the next arc.
642      ///
643      /// This function gives back the next arc in the iteration order.
644      void next(Arc&) const {}
645
646      /// \brief Return the first arc incomming to the given node.
647      ///
648      /// This function gives back the first arc incomming to the
649      /// given node.
650      void firstIn(Arc&, const Node&) const {}
651
652      /// \brief Return the next arc incomming to the given node.
653      ///
654      /// This function gives back the next arc incomming to the
655      /// given node.
656      void nextIn(Arc&) const {}
657
658      /// \brief Return the first arc outgoing form the given node.
659      ///
660      /// This function gives back the first arc outgoing form the
661      /// given node.
662      void firstOut(Arc&, const Node&) const {}
663
664      /// \brief Return the next arc outgoing form the given node.
665      ///
666      /// This function gives back the next arc outgoing form the
667      /// given node.
668      void nextOut(Arc&) const {}
669
670      /// @}
671
672      /// \name Class Based Iteration
673      ///
674      /// This interface provides iterator classes for digraph items.
675      ///
676      /// @{
677
678      /// \brief This iterator goes through each node.
679      ///
680      /// This iterator goes through each node.
681      ///
682      typedef GraphItemIt<Digraph, Node> NodeIt;
683
684      /// \brief This iterator goes through each arc.
685      ///
686      /// This iterator goes through each arc.
687      ///
688      typedef GraphItemIt<Digraph, Arc> ArcIt;
689
690      /// \brief This iterator goes trough the incoming arcs of a node.
691      ///
692      /// This iterator goes trough the \e incoming arcs of a certain node
693      /// of a digraph.
694      typedef GraphIncIt<Digraph, Arc, Node, 'i'> InArcIt;
695
696      /// \brief This iterator goes trough the outgoing arcs of a node.
697      ///
698      /// This iterator goes trough the \e outgoing arcs of a certain node
699      /// of a digraph.
700      typedef GraphIncIt<Digraph, Arc, Node, 'o'> OutArcIt;
701
702      /// \brief The base node of the iterator.
703      ///
704      /// This function gives back the base node of the iterator.
705      /// It is always the target node of the pointed arc.
706      Node baseNode(const InArcIt&) const { return INVALID; }
707
708      /// \brief The running node of the iterator.
709      ///
710      /// This function gives back the running node of the iterator.
711      /// It is always the source node of the pointed arc.
712      Node runningNode(const InArcIt&) const { return INVALID; }
713
714      /// \brief The base node of the iterator.
715      ///
716      /// This function gives back the base node of the iterator.
717      /// It is always the source node of the pointed arc.
718      Node baseNode(const OutArcIt&) const { return INVALID; }
719
720      /// \brief The running node of the iterator.
721      ///
722      /// This function gives back the running node of the iterator.
723      /// It is always the target node of the pointed arc.
724      Node runningNode(const OutArcIt&) const { return INVALID; }
725
726      /// @}
727
728      template <typename _Digraph>
729      struct Constraints {
730        void constraints() {
731          checkConcept<Base, _Digraph>();
732
733          {
734            typename _Digraph::Node node(INVALID);
735            typename _Digraph::Arc arc(INVALID);
736            {
737              digraph.first(node);
738              digraph.next(node);
739            }
740            {
741              digraph.first(arc);
742              digraph.next(arc);
743            }
744            {
745              digraph.firstIn(arc, node);
746              digraph.nextIn(arc);
747            }
748            {
749              digraph.firstOut(arc, node);
750              digraph.nextOut(arc);
751            }
752          }
753
754          {
755            checkConcept<GraphItemIt<_Digraph, typename _Digraph::Arc>,
756              typename _Digraph::ArcIt >();
757            checkConcept<GraphItemIt<_Digraph, typename _Digraph::Node>,
758              typename _Digraph::NodeIt >();
759            checkConcept<GraphIncIt<_Digraph, typename _Digraph::Arc,
760              typename _Digraph::Node, 'i'>, typename _Digraph::InArcIt>();
761            checkConcept<GraphIncIt<_Digraph, typename _Digraph::Arc,
762              typename _Digraph::Node, 'o'>, typename _Digraph::OutArcIt>();
763
764            typename _Digraph::Node n;
765            const typename _Digraph::InArcIt iait(INVALID);
766            const typename _Digraph::OutArcIt oait(INVALID);
767            n = digraph.baseNode(iait);
768            n = digraph.runningNode(iait);
769            n = digraph.baseNode(oait);
770            n = digraph.runningNode(oait);
771            ignore_unused_variable_warning(n);
772          }
773        }
774
775        const _Digraph& digraph;
776        Constraints() {}
777      };
778    };
779
780    /// \brief Skeleton class for iterable undirected graphs.
781    ///
782    /// This class describes the interface of iterable undirected
783    /// graphs. It extends \ref IterableDigraphComponent with the core
784    /// iterable interface of undirected graphs.
785    /// This concept is part of the Graph concept.
786    template <typename BAS = BaseGraphComponent>
787    class IterableGraphComponent : public IterableDigraphComponent<BAS> {
788    public:
789
790      typedef BAS Base;
791      typedef typename Base::Node Node;
792      typedef typename Base::Arc Arc;
793      typedef typename Base::Edge Edge;
794
795
796      typedef IterableGraphComponent Graph;
797
798      /// \name Base Iteration
799      ///
800      /// This interface provides functions for iteration on edges.
801      ///
802      /// @{
803
804      using IterableDigraphComponent<Base>::first;
805      using IterableDigraphComponent<Base>::next;
806
807      /// \brief Return the first edge.
808      ///
809      /// This function gives back the first edge in the iteration order.
810      void first(Edge&) const {}
811
812      /// \brief Return the next edge.
813      ///
814      /// This function gives back the next edge in the iteration order.
815      void next(Edge&) const {}
816
817      /// \brief Return the first edge incident to the given node.
818      ///
819      /// This function gives back the first edge incident to the given
820      /// node. The bool parameter gives back the direction for which the
821      /// source node of the directed arc representing the edge is the
822      /// given node.
823      void firstInc(Edge&, bool&, const Node&) const {}
824
825      /// \brief Gives back the next of the edges from the
826      /// given node.
827      ///
828      /// This function gives back the next edge incident to the given
829      /// node. The bool parameter should be used as \c firstInc() use it.
830      void nextInc(Edge&, bool&) const {}
831
832      using IterableDigraphComponent<Base>::baseNode;
833      using IterableDigraphComponent<Base>::runningNode;
834
835      /// @}
836
837      /// \name Class Based Iteration
838      ///
839      /// This interface provides iterator classes for edges.
840      ///
841      /// @{
842
843      /// \brief This iterator goes through each edge.
844      ///
845      /// This iterator goes through each edge.
846      typedef GraphItemIt<Graph, Edge> EdgeIt;
847
848      /// \brief This iterator goes trough the incident edges of a
849      /// node.
850      ///
851      /// This iterator goes trough the incident edges of a certain
852      /// node of a graph.
853      typedef GraphIncIt<Graph, Edge, Node, 'e'> IncEdgeIt;
854
855      /// \brief The base node of the iterator.
856      ///
857      /// This function gives back the base node of the iterator.
858      Node baseNode(const IncEdgeIt&) const { return INVALID; }
859
860      /// \brief The running node of the iterator.
861      ///
862      /// This function gives back the running node of the iterator.
863      Node runningNode(const IncEdgeIt&) const { return INVALID; }
864
865      /// @}
866
867      template <typename _Graph>
868      struct Constraints {
869        void constraints() {
870          checkConcept<IterableDigraphComponent<Base>, _Graph>();
871
872          {
873            typename _Graph::Node node(INVALID);
874            typename _Graph::Edge edge(INVALID);
875            bool dir;
876            {
877              graph.first(edge);
878              graph.next(edge);
879            }
880            {
881              graph.firstInc(edge, dir, node);
882              graph.nextInc(edge, dir);
883            }
884
885          }
886
887          {
888            checkConcept<GraphItemIt<_Graph, typename _Graph::Edge>,
889              typename _Graph::EdgeIt >();
890            checkConcept<GraphIncIt<_Graph, typename _Graph::Edge,
891              typename _Graph::Node, 'e'>, typename _Graph::IncEdgeIt>();
892
893            typename _Graph::Node n;
894            const typename _Graph::IncEdgeIt ieit(INVALID);
895            n = graph.baseNode(ieit);
896            n = graph.runningNode(ieit);
897          }
898        }
899
900        const _Graph& graph;
901        Constraints() {}
902      };
903    };
904
905    /// \brief Skeleton class for alterable directed graphs.
906    ///
907    /// This class describes the interface of alterable directed
908    /// graphs. It extends \ref BaseDigraphComponent with the alteration
909    /// notifier interface. It implements
910    /// an observer-notifier pattern for each digraph item. More
911    /// obsevers can be registered into the notifier and whenever an
912    /// alteration occured in the digraph all the observers will be
913    /// notified about it.
914    template <typename BAS = BaseDigraphComponent>
915    class AlterableDigraphComponent : public BAS {
916    public:
917
918      typedef BAS Base;
919      typedef typename Base::Node Node;
920      typedef typename Base::Arc Arc;
921
922
923      /// Node alteration notifier class.
924      typedef AlterationNotifier<AlterableDigraphComponent, Node>
925      NodeNotifier;
926      /// Arc alteration notifier class.
927      typedef AlterationNotifier<AlterableDigraphComponent, Arc>
928      ArcNotifier;
929
930      /// \brief Return the node alteration notifier.
931      ///
932      /// This function gives back the node alteration notifier.
933      NodeNotifier& notifier(Node) const {
934         return NodeNotifier();
935      }
936
937      /// \brief Return the arc alteration notifier.
938      ///
939      /// This function gives back the arc alteration notifier.
940      ArcNotifier& notifier(Arc) const {
941        return ArcNotifier();
942      }
943
944      template <typename _Digraph>
945      struct Constraints {
946        void constraints() {
947          checkConcept<Base, _Digraph>();
948          typename _Digraph::NodeNotifier& nn
949            = digraph.notifier(typename _Digraph::Node());
950
951          typename _Digraph::ArcNotifier& en
952            = digraph.notifier(typename _Digraph::Arc());
953
954          ignore_unused_variable_warning(nn);
955          ignore_unused_variable_warning(en);
956        }
957
958        const _Digraph& digraph;
959        Constraints() {}
960      };
961    };
962
963    /// \brief Skeleton class for alterable undirected graphs.
964    ///
965    /// This class describes the interface of alterable undirected
966    /// graphs. It extends \ref AlterableDigraphComponent with the alteration
967    /// notifier interface of undirected graphs. It implements
968    /// an observer-notifier pattern for the edges. More
969    /// obsevers can be registered into the notifier and whenever an
970    /// alteration occured in the graph all the observers will be
971    /// notified about it.
972    template <typename BAS = BaseGraphComponent>
973    class AlterableGraphComponent : public AlterableDigraphComponent<BAS> {
974    public:
975
976      typedef BAS Base;
977      typedef typename Base::Edge Edge;
978
979
980      /// Edge alteration notifier class.
981      typedef AlterationNotifier<AlterableGraphComponent, Edge>
982      EdgeNotifier;
983
984      /// \brief Return the edge alteration notifier.
985      ///
986      /// This function gives back the edge alteration notifier.
987      EdgeNotifier& notifier(Edge) const {
988        return EdgeNotifier();
989      }
990
991      template <typename _Graph>
992      struct Constraints {
993        void constraints() {
994          checkConcept<AlterableDigraphComponent<Base>, _Graph>();
995          typename _Graph::EdgeNotifier& uen
996            = graph.notifier(typename _Graph::Edge());
997          ignore_unused_variable_warning(uen);
998        }
999
1000        const _Graph& graph;
1001        Constraints() {}
1002      };
1003    };
1004
1005    /// \brief Concept class for standard graph maps.
1006    ///
1007    /// This class describes the concept of standard graph maps, i.e.
1008    /// the \c NodeMap, \c ArcMap and \c EdgeMap subtypes of digraph and
1009    /// graph types, which can be used for associating data to graph items.
1010    /// The standard graph maps must conform to the ReferenceMap concept.
1011    template <typename GR, typename K, typename V>
1012    class GraphMap : public ReferenceMap<K, V, V&, const V&> {
1013      typedef ReferenceMap<K, V, V&, const V&> Parent;
1014
1015    public:
1016
1017      /// The key type of the map.
1018      typedef K Key;
1019      /// The value type of the map.
1020      typedef V Value;
1021      /// The reference type of the map.
1022      typedef Value& Reference;
1023      /// The const reference type of the map.
1024      typedef const Value& ConstReference;
1025
1026      // The reference map tag.
1027      typedef True ReferenceMapTag;
1028
1029      /// \brief Construct a new map.
1030      ///
1031      /// Construct a new map for the graph.
1032      explicit GraphMap(const GR&) {}
1033      /// \brief Construct a new map with default value.
1034      ///
1035      /// Construct a new map for the graph and initalize the values.
1036      GraphMap(const GR&, const Value&) {}
1037
1038    private:
1039      /// \brief Copy constructor.
1040      ///
1041      /// Copy Constructor.
1042      GraphMap(const GraphMap&) : Parent() {}
1043
1044      /// \brief Assignment operator.
1045      ///
1046      /// Assignment operator. It does not mofify the underlying graph,
1047      /// it just iterates on the current item set and set the  map
1048      /// with the value returned by the assigned map.
1049      template <typename CMap>
1050      GraphMap& operator=(const CMap&) {
1051        checkConcept<ReadMap<Key, Value>, CMap>();
1052        return *this;
1053      }
1054
1055    public:
1056      template<typename _Map>
1057      struct Constraints {
1058        void constraints() {
1059          checkConcept
1060            <ReferenceMap<Key, Value, Value&, const Value&>, _Map>();
1061          _Map m1(g);
1062          _Map m2(g,t);
1063         
1064          // Copy constructor
1065          // _Map m3(m);
1066
1067          // Assignment operator
1068          // ReadMap<Key, Value> cmap;
1069          // m3 = cmap;
1070
1071          ignore_unused_variable_warning(m1);
1072          ignore_unused_variable_warning(m2);
1073          // ignore_unused_variable_warning(m3);
1074        }
1075
1076        const _Map &m;
1077        const GR &g;
1078        const typename GraphMap::Value &t;
1079        Constraints() {}
1080      };
1081
1082    };
1083
1084    /// \brief Skeleton class for mappable directed graphs.
1085    ///
1086    /// This class describes the interface of mappable directed graphs.
1087    /// It extends \ref BaseDigraphComponent with the standard digraph
1088    /// map classes, namely \c NodeMap and \c ArcMap.
1089    /// This concept is part of the Digraph concept.
1090    template <typename BAS = BaseDigraphComponent>
1091    class MappableDigraphComponent : public BAS  {
1092    public:
1093
1094      typedef BAS Base;
1095      typedef typename Base::Node Node;
1096      typedef typename Base::Arc Arc;
1097
1098      typedef MappableDigraphComponent Digraph;
1099
1100      /// \brief Standard graph map for the nodes.
1101      ///
1102      /// Standard graph map for the nodes.
1103      /// It conforms to the ReferenceMap concept.
1104      template <typename V>
1105      class NodeMap : public GraphMap<MappableDigraphComponent, Node, V> {
1106        typedef GraphMap<MappableDigraphComponent, Node, V> Parent;
1107
1108      public:
1109        /// \brief Construct a new map.
1110        ///
1111        /// Construct a new map for the digraph.
1112        explicit NodeMap(const MappableDigraphComponent& digraph)
1113          : Parent(digraph) {}
1114
1115        /// \brief Construct a new map with default value.
1116        ///
1117        /// Construct a new map for the digraph and initalize the values.
1118        NodeMap(const MappableDigraphComponent& digraph, const V& value)
1119          : Parent(digraph, value) {}
1120
1121      private:
1122        /// \brief Copy constructor.
1123        ///
1124        /// Copy Constructor.
1125        NodeMap(const NodeMap& nm) : Parent(nm) {}
1126
1127        /// \brief Assignment operator.
1128        ///
1129        /// Assignment operator.
1130        template <typename CMap>
1131        NodeMap& operator=(const CMap&) {
1132          checkConcept<ReadMap<Node, V>, CMap>();
1133          return *this;
1134        }
1135
1136      };
1137
1138      /// \brief Standard graph map for the arcs.
1139      ///
1140      /// Standard graph map for the arcs.
1141      /// It conforms to the ReferenceMap concept.
1142      template <typename V>
1143      class ArcMap : public GraphMap<MappableDigraphComponent, Arc, V> {
1144        typedef GraphMap<MappableDigraphComponent, Arc, V> Parent;
1145
1146      public:
1147        /// \brief Construct a new map.
1148        ///
1149        /// Construct a new map for the digraph.
1150        explicit ArcMap(const MappableDigraphComponent& digraph)
1151          : Parent(digraph) {}
1152
1153        /// \brief Construct a new map with default value.
1154        ///
1155        /// Construct a new map for the digraph and initalize the values.
1156        ArcMap(const MappableDigraphComponent& digraph, const V& value)
1157          : Parent(digraph, value) {}
1158
1159      private:
1160        /// \brief Copy constructor.
1161        ///
1162        /// Copy Constructor.
1163        ArcMap(const ArcMap& nm) : Parent(nm) {}
1164
1165        /// \brief Assignment operator.
1166        ///
1167        /// Assignment operator.
1168        template <typename CMap>
1169        ArcMap& operator=(const CMap&) {
1170          checkConcept<ReadMap<Arc, V>, CMap>();
1171          return *this;
1172        }
1173
1174      };
1175
1176
1177      template <typename _Digraph>
1178      struct Constraints {
1179
1180        struct Dummy {
1181          int value;
1182          Dummy() : value(0) {}
1183          Dummy(int _v) : value(_v) {}
1184        };
1185
1186        void constraints() {
1187          checkConcept<Base, _Digraph>();
1188          { // int map test
1189            typedef typename _Digraph::template NodeMap<int> IntNodeMap;
1190            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, int>,
1191              IntNodeMap >();
1192          } { // bool map test
1193            typedef typename _Digraph::template NodeMap<bool> BoolNodeMap;
1194            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, bool>,
1195              BoolNodeMap >();
1196          } { // Dummy map test
1197            typedef typename _Digraph::template NodeMap<Dummy> DummyNodeMap;
1198            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, Dummy>,
1199              DummyNodeMap >();
1200          }
1201
1202          { // int map test
1203            typedef typename _Digraph::template ArcMap<int> IntArcMap;
1204            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, int>,
1205              IntArcMap >();
1206          } { // bool map test
1207            typedef typename _Digraph::template ArcMap<bool> BoolArcMap;
1208            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, bool>,
1209              BoolArcMap >();
1210          } { // Dummy map test
1211            typedef typename _Digraph::template ArcMap<Dummy> DummyArcMap;
1212            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, Dummy>,
1213              DummyArcMap >();
1214          }
1215        }
1216
1217        const _Digraph& digraph;
1218        Constraints() {}
1219      };
1220    };
1221
1222    /// \brief Skeleton class for mappable undirected graphs.
1223    ///
1224    /// This class describes the interface of mappable undirected graphs.
1225    /// It extends \ref MappableDigraphComponent with the standard graph
1226    /// map class for edges (\c EdgeMap).
1227    /// This concept is part of the Graph concept.
1228    template <typename BAS = BaseGraphComponent>
1229    class MappableGraphComponent : public MappableDigraphComponent<BAS>  {
1230    public:
1231
1232      typedef BAS Base;
1233      typedef typename Base::Edge Edge;
1234
1235      typedef MappableGraphComponent Graph;
1236
1237      /// \brief Standard graph map for the edges.
1238      ///
1239      /// Standard graph map for the edges.
1240      /// It conforms to the ReferenceMap concept.
1241      template <typename V>
1242      class EdgeMap : public GraphMap<MappableGraphComponent, Edge, V> {
1243        typedef GraphMap<MappableGraphComponent, Edge, V> Parent;
1244
1245      public:
1246        /// \brief Construct a new map.
1247        ///
1248        /// Construct a new map for the graph.
1249        explicit EdgeMap(const MappableGraphComponent& graph)
1250          : Parent(graph) {}
1251
1252        /// \brief Construct a new map with default value.
1253        ///
1254        /// Construct a new map for the graph and initalize the values.
1255        EdgeMap(const MappableGraphComponent& graph, const V& value)
1256          : Parent(graph, value) {}
1257
1258      private:
1259        /// \brief Copy constructor.
1260        ///
1261        /// Copy Constructor.
1262        EdgeMap(const EdgeMap& nm) : Parent(nm) {}
1263
1264        /// \brief Assignment operator.
1265        ///
1266        /// Assignment operator.
1267        template <typename CMap>
1268        EdgeMap& operator=(const CMap&) {
1269          checkConcept<ReadMap<Edge, V>, CMap>();
1270          return *this;
1271        }
1272
1273      };
1274
1275
1276      template <typename _Graph>
1277      struct Constraints {
1278
1279        struct Dummy {
1280          int value;
1281          Dummy() : value(0) {}
1282          Dummy(int _v) : value(_v) {}
1283        };
1284
1285        void constraints() {
1286          checkConcept<MappableDigraphComponent<Base>, _Graph>();
1287
1288          { // int map test
1289            typedef typename _Graph::template EdgeMap<int> IntEdgeMap;
1290            checkConcept<GraphMap<_Graph, typename _Graph::Edge, int>,
1291              IntEdgeMap >();
1292          } { // bool map test
1293            typedef typename _Graph::template EdgeMap<bool> BoolEdgeMap;
1294            checkConcept<GraphMap<_Graph, typename _Graph::Edge, bool>,
1295              BoolEdgeMap >();
1296          } { // Dummy map test
1297            typedef typename _Graph::template EdgeMap<Dummy> DummyEdgeMap;
1298            checkConcept<GraphMap<_Graph, typename _Graph::Edge, Dummy>,
1299              DummyEdgeMap >();
1300          }
1301        }
1302
1303        const _Graph& graph;
1304        Constraints() {}
1305      };
1306    };
1307
1308    /// \brief Skeleton class for extendable directed graphs.
1309    ///
1310    /// This class describes the interface of extendable directed graphs.
1311    /// It extends \ref BaseDigraphComponent with functions for adding
1312    /// nodes and arcs to the digraph.
1313    /// This concept requires \ref AlterableDigraphComponent.
1314    template <typename BAS = BaseDigraphComponent>
1315    class ExtendableDigraphComponent : public BAS {
1316    public:
1317      typedef BAS Base;
1318
1319      typedef typename Base::Node Node;
1320      typedef typename Base::Arc Arc;
1321
1322      /// \brief Add a new node to the digraph.
1323      ///
1324      /// This function adds a new node to the digraph.
1325      Node addNode() {
1326        return INVALID;
1327      }
1328
1329      /// \brief Add a new arc connecting the given two nodes.
1330      ///
1331      /// This function adds a new arc connecting the given two nodes
1332      /// of the digraph.
1333      Arc addArc(const Node&, const Node&) {
1334        return INVALID;
1335      }
1336
1337      template <typename _Digraph>
1338      struct Constraints {
1339        void constraints() {
1340          checkConcept<Base, _Digraph>();
1341          typename _Digraph::Node node_a, node_b;
1342          node_a = digraph.addNode();
1343          node_b = digraph.addNode();
1344          typename _Digraph::Arc arc;
1345          arc = digraph.addArc(node_a, node_b);
1346        }
1347
1348        _Digraph& digraph;
1349        Constraints() {}
1350      };
1351    };
1352
1353    /// \brief Skeleton class for extendable undirected graphs.
1354    ///
1355    /// This class describes the interface of extendable undirected graphs.
1356    /// It extends \ref BaseGraphComponent with functions for adding
1357    /// nodes and edges to the graph.
1358    /// This concept requires \ref AlterableGraphComponent.
1359    template <typename BAS = BaseGraphComponent>
1360    class ExtendableGraphComponent : public BAS {
1361    public:
1362
1363      typedef BAS Base;
1364      typedef typename Base::Node Node;
1365      typedef typename Base::Edge Edge;
1366
1367      /// \brief Add a new node to the digraph.
1368      ///
1369      /// This function adds a new node to the digraph.
1370      Node addNode() {
1371        return INVALID;
1372      }
1373
1374      /// \brief Add a new edge connecting the given two nodes.
1375      ///
1376      /// This function adds a new edge connecting the given two nodes
1377      /// of the graph.
1378      Edge addEdge(const Node&, const Node&) {
1379        return INVALID;
1380      }
1381
1382      template <typename _Graph>
1383      struct Constraints {
1384        void constraints() {
1385          checkConcept<Base, _Graph>();
1386          typename _Graph::Node node_a, node_b;
1387          node_a = graph.addNode();
1388          node_b = graph.addNode();
1389          typename _Graph::Edge edge;
1390          edge = graph.addEdge(node_a, node_b);
1391        }
1392
1393        _Graph& graph;
1394        Constraints() {}
1395      };
1396    };
1397
1398    /// \brief Skeleton class for erasable directed graphs.
1399    ///
1400    /// This class describes the interface of erasable directed graphs.
1401    /// It extends \ref BaseDigraphComponent with functions for removing
1402    /// nodes and arcs from the digraph.
1403    /// This concept requires \ref AlterableDigraphComponent.
1404    template <typename BAS = BaseDigraphComponent>
1405    class ErasableDigraphComponent : public BAS {
1406    public:
1407
1408      typedef BAS Base;
1409      typedef typename Base::Node Node;
1410      typedef typename Base::Arc Arc;
1411
1412      /// \brief Erase a node from the digraph.
1413      ///
1414      /// This function erases the given node from the digraph and all arcs
1415      /// connected to the node.
1416      void erase(const Node&) {}
1417
1418      /// \brief Erase an arc from the digraph.
1419      ///
1420      /// This function erases the given arc from the digraph.
1421      void erase(const Arc&) {}
1422
1423      template <typename _Digraph>
1424      struct Constraints {
1425        void constraints() {
1426          checkConcept<Base, _Digraph>();
1427          const typename _Digraph::Node node(INVALID);
1428          digraph.erase(node);
1429          const typename _Digraph::Arc arc(INVALID);
1430          digraph.erase(arc);
1431        }
1432
1433        _Digraph& digraph;
1434        Constraints() {}
1435      };
1436    };
1437
1438    /// \brief Skeleton class for erasable undirected graphs.
1439    ///
1440    /// This class describes the interface of erasable undirected graphs.
1441    /// It extends \ref BaseGraphComponent with functions for removing
1442    /// nodes and edges from the graph.
1443    /// This concept requires \ref AlterableGraphComponent.
1444    template <typename BAS = BaseGraphComponent>
1445    class ErasableGraphComponent : public BAS {
1446    public:
1447
1448      typedef BAS Base;
1449      typedef typename Base::Node Node;
1450      typedef typename Base::Edge Edge;
1451
1452      /// \brief Erase a node from the graph.
1453      ///
1454      /// This function erases the given node from the graph and all edges
1455      /// connected to the node.
1456      void erase(const Node&) {}
1457
1458      /// \brief Erase an edge from the digraph.
1459      ///
1460      /// This function erases the given edge from the digraph.
1461      void erase(const Edge&) {}
1462
1463      template <typename _Graph>
1464      struct Constraints {
1465        void constraints() {
1466          checkConcept<Base, _Graph>();
1467          const typename _Graph::Node node(INVALID);
1468          graph.erase(node);
1469          const typename _Graph::Edge edge(INVALID);
1470          graph.erase(edge);
1471        }
1472
1473        _Graph& graph;
1474        Constraints() {}
1475      };
1476    };
1477
1478    /// \brief Skeleton class for clearable directed graphs.
1479    ///
1480    /// This class describes the interface of clearable directed graphs.
1481    /// It extends \ref BaseDigraphComponent with a function for clearing
1482    /// the digraph.
1483    /// This concept requires \ref AlterableDigraphComponent.
1484    template <typename BAS = BaseDigraphComponent>
1485    class ClearableDigraphComponent : public BAS {
1486    public:
1487
1488      typedef BAS Base;
1489
1490      /// \brief Erase all nodes and arcs from the digraph.
1491      ///
1492      /// This function erases all nodes and arcs from the digraph.
1493      void clear() {}
1494
1495      template <typename _Digraph>
1496      struct Constraints {
1497        void constraints() {
1498          checkConcept<Base, _Digraph>();
1499          digraph.clear();
1500        }
1501
1502        _Digraph& digraph;
1503        Constraints() {}
1504      };
1505    };
1506
1507    /// \brief Skeleton class for clearable undirected graphs.
1508    ///
1509    /// This class describes the interface of clearable undirected graphs.
1510    /// It extends \ref BaseGraphComponent with a function for clearing
1511    /// the graph.
1512    /// This concept requires \ref AlterableGraphComponent.
1513    template <typename BAS = BaseGraphComponent>
1514    class ClearableGraphComponent : public ClearableDigraphComponent<BAS> {
1515    public:
1516
1517      typedef BAS Base;
1518
1519      /// \brief Erase all nodes and edges from the graph.
1520      ///
1521      /// This function erases all nodes and edges from the graph.
1522      void clear() {}
1523
1524      template <typename _Graph>
1525      struct Constraints {
1526        void constraints() {
1527          checkConcept<Base, _Graph>();
1528          graph.clear();
1529        }
1530
1531        _Graph& graph;
1532        Constraints() {}
1533      };
1534    };
1535
1536  }
1537
1538}
1539
1540#endif
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