COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/concepts/graph_components.h @ 617:4137ef9aacc6

Last change on this file since 617:4137ef9aacc6 was 617:4137ef9aacc6, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Fix and uniform the usage of Graph and Parent typedefs (#268)

  • Rename Graph typedefs to GraphType? in the implementation of graph maps and MapExtender? to prevent conflicts (especially using VS). They are not public.
  • Make Parent typedefs private in all classes.
  • Replace Digraph with Graph in some places (fix faulty renamings of the script).
  • Use Graph and Digraph typedefs (more) consequently.
File size: 47.9 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 Equality operator.
75      ///
76      /// Equality operator.
77      bool operator==(const GraphItem&) const { return false; }
78
79      /// \brief Inequality operator.
80      ///
81      /// Inequality operator.
82      bool operator!=(const GraphItem&) const { return false; }
83
84      /// \brief Ordering operator.
85      ///
86      /// This operator defines an ordering of the items.
87      /// It makes possible to use graph item types as key types in
88      /// associative containers (e.g. \c std::map).
89      ///
90      /// \note This operator only have to define some strict ordering of
91      /// the items; this order has nothing to do with the iteration
92      /// ordering of the items.
93      bool operator<(const GraphItem&) const { return false; }
94
95      template<typename _GraphItem>
96      struct Constraints {
97        void constraints() {
98          _GraphItem i1;
99          _GraphItem i2 = i1;
100          _GraphItem i3 = INVALID;
101
102          i1 = i2 = i3;
103
104          bool b;
105          b = (ia == ib) && (ia != ib);
106          b = (ia == INVALID) && (ib != INVALID);
107          b = (ia < ib);
108        }
109
110        const _GraphItem &ia;
111        const _GraphItem &ib;
112      };
113    };
114
115    /// \brief Base skeleton class for directed graphs.
116    ///
117    /// This class describes the base interface of directed graph types.
118    /// All digraph %concepts have to conform to this class.
119    /// It just provides types for nodes and arcs and functions
120    /// to get the source and the target nodes of arcs.
121    class BaseDigraphComponent {
122    public:
123
124      typedef BaseDigraphComponent Digraph;
125
126      /// \brief Node class of the digraph.
127      ///
128      /// This class represents the nodes of the digraph.
129      typedef GraphItem<'n'> Node;
130
131      /// \brief Arc class of the digraph.
132      ///
133      /// This class represents the arcs of the digraph.
134      typedef GraphItem<'a'> Arc;
135
136      /// \brief Return the source node of an arc.
137      ///
138      /// This function returns the source node of an arc.
139      Node source(const Arc&) const { return INVALID; }
140
141      /// \brief Return the target node of an arc.
142      ///
143      /// This function returns the target node of an arc.
144      Node target(const Arc&) const { return INVALID; }
145
146      /// \brief Return the opposite node on the given arc.
147      ///
148      /// This function returns the opposite node on the given arc.
149      Node oppositeNode(const Node&, const Arc&) const {
150        return INVALID;
151      }
152
153      template <typename _Digraph>
154      struct Constraints {
155        typedef typename _Digraph::Node Node;
156        typedef typename _Digraph::Arc Arc;
157
158        void constraints() {
159          checkConcept<GraphItem<'n'>, Node>();
160          checkConcept<GraphItem<'a'>, Arc>();
161          {
162            Node n;
163            Arc e(INVALID);
164            n = digraph.source(e);
165            n = digraph.target(e);
166            n = digraph.oppositeNode(n, e);
167          }
168        }
169
170        const _Digraph& digraph;
171      };
172    };
173
174    /// \brief Base skeleton class for undirected graphs.
175    ///
176    /// This class describes the base interface of undirected graph types.
177    /// All graph %concepts have to conform to this class.
178    /// It extends the interface of \ref BaseDigraphComponent with an
179    /// \c Edge type and functions to get the end nodes of edges,
180    /// to convert from arcs to edges and to get both direction of edges.
181    class BaseGraphComponent : public BaseDigraphComponent {
182    public:
183
184      typedef BaseGraphComponent Graph;
185
186      typedef BaseDigraphComponent::Node Node;
187      typedef BaseDigraphComponent::Arc Arc;
188
189      /// \brief Undirected edge class of the graph.
190      ///
191      /// This class represents the undirected edges of the graph.
192      /// Undirected graphs can be used as directed graphs, each edge is
193      /// represented by two opposite directed arcs.
194      class Edge : public GraphItem<'e'> {
195        typedef GraphItem<'e'> Parent;
196
197      public:
198        /// \brief Default constructor.
199        ///
200        /// Default constructor.
201        /// \warning The default constructor is not required to set
202        /// the item to some well-defined value. So you should consider it
203        /// as uninitialized.
204        Edge() {}
205
206        /// \brief Copy constructor.
207        ///
208        /// Copy constructor.
209        Edge(const Edge &) : Parent() {}
210
211        /// \brief Constructor for conversion from \c INVALID.
212        ///
213        /// Constructor for conversion from \c INVALID.
214        /// It initializes the item to be invalid.
215        /// \sa Invalid for more details.
216        Edge(Invalid) {}
217
218        /// \brief Constructor for conversion from an arc.
219        ///
220        /// Constructor for conversion from an arc.
221        /// Besides the core graph item functionality each arc should
222        /// be convertible to the represented edge.
223        Edge(const Arc&) {}
224
225        /// \brief Assign an arc to an edge.
226        ///
227        /// This function assigns an arc to an edge.
228        /// Besides the core graph item functionality each arc should
229        /// be convertible to the represented edge.
230        Edge& operator=(const Arc&) { return *this; }
231      };
232
233      /// \brief Return one end node of an edge.
234      ///
235      /// This function returns one end node of an edge.
236      Node u(const Edge&) const { return INVALID; }
237
238      /// \brief Return the other end node of an edge.
239      ///
240      /// This function returns the other end node of an edge.
241      Node v(const Edge&) const { return INVALID; }
242
243      /// \brief Return a directed arc related to an edge.
244      ///
245      /// This function returns a directed arc from its direction and the
246      /// represented edge.
247      Arc direct(const Edge&, bool) const { return INVALID; }
248
249      /// \brief Return a directed arc related to an edge.
250      ///
251      /// This function returns a directed arc from its source node and the
252      /// represented edge.
253      Arc direct(const Edge&, const Node&) const { return INVALID; }
254
255      /// \brief Return the direction of the arc.
256      ///
257      /// Returns the direction of the arc. Each arc represents an
258      /// edge with a direction. It gives back the
259      /// direction.
260      bool direction(const Arc&) const { return true; }
261
262      /// \brief Return the opposite arc.
263      ///
264      /// This function returns the opposite arc, i.e. the arc representing
265      /// the same edge and has opposite direction.
266      Arc oppositeArc(const Arc&) const { return INVALID; }
267
268      template <typename _Graph>
269      struct Constraints {
270        typedef typename _Graph::Node Node;
271        typedef typename _Graph::Arc Arc;
272        typedef typename _Graph::Edge Edge;
273
274        void constraints() {
275          checkConcept<BaseDigraphComponent, _Graph>();
276          checkConcept<GraphItem<'e'>, Edge>();
277          {
278            Node n;
279            Edge ue(INVALID);
280            Arc e;
281            n = graph.u(ue);
282            n = graph.v(ue);
283            e = graph.direct(ue, true);
284            e = graph.direct(ue, false);
285            e = graph.direct(ue, n);
286            e = graph.oppositeArc(e);
287            ue = e;
288            bool d = graph.direction(e);
289            ignore_unused_variable_warning(d);
290          }
291        }
292
293        const _Graph& graph;
294      };
295
296    };
297
298    /// \brief Skeleton class for \e idable directed graphs.
299    ///
300    /// This class describes the interface of \e idable directed graphs.
301    /// It extends \ref BaseDigraphComponent with the core ID functions.
302    /// The ids of the items must be unique and immutable.
303    /// This concept is part of the Digraph concept.
304    template <typename BAS = BaseDigraphComponent>
305    class IDableDigraphComponent : public BAS {
306    public:
307
308      typedef BAS Base;
309      typedef typename Base::Node Node;
310      typedef typename Base::Arc Arc;
311
312      /// \brief Return a unique integer id for the given node.
313      ///
314      /// This function returns a unique integer id for the given node.
315      int id(const Node&) const { return -1; }
316
317      /// \brief Return the node by its unique id.
318      ///
319      /// This function returns the node by its unique id.
320      /// If the digraph does not contain a node with the given id,
321      /// then the result of the function is undefined.
322      Node nodeFromId(int) const { return INVALID; }
323
324      /// \brief Return a unique integer id for the given arc.
325      ///
326      /// This function returns a unique integer id for the given arc.
327      int id(const Arc&) const { return -1; }
328
329      /// \brief Return the arc by its unique id.
330      ///
331      /// This function returns the arc by its unique id.
332      /// If the digraph does not contain an arc with the given id,
333      /// then the result of the function is undefined.
334      Arc arcFromId(int) const { return INVALID; }
335
336      /// \brief Return an integer greater or equal to the maximum
337      /// node id.
338      ///
339      /// This function returns an integer greater or equal to the
340      /// maximum node id.
341      int maxNodeId() const { return -1; }
342
343      /// \brief Return an integer greater or equal to the maximum
344      /// arc id.
345      ///
346      /// This function returns an integer greater or equal to the
347      /// maximum arc id.
348      int maxArcId() const { return -1; }
349
350      template <typename _Digraph>
351      struct Constraints {
352
353        void constraints() {
354          checkConcept<Base, _Digraph >();
355          typename _Digraph::Node node;
356          int nid = digraph.id(node);
357          nid = digraph.id(node);
358          node = digraph.nodeFromId(nid);
359          typename _Digraph::Arc arc;
360          int eid = digraph.id(arc);
361          eid = digraph.id(arc);
362          arc = digraph.arcFromId(eid);
363
364          nid = digraph.maxNodeId();
365          ignore_unused_variable_warning(nid);
366          eid = digraph.maxArcId();
367          ignore_unused_variable_warning(eid);
368        }
369
370        const _Digraph& digraph;
371      };
372    };
373
374    /// \brief Skeleton class for \e idable undirected graphs.
375    ///
376    /// This class describes the interface of \e idable undirected
377    /// graphs. It extends \ref IDableDigraphComponent with the core ID
378    /// functions of undirected graphs.
379    /// The ids of the items must be unique and immutable.
380    /// This concept is part of the Graph concept.
381    template <typename BAS = BaseGraphComponent>
382    class IDableGraphComponent : public IDableDigraphComponent<BAS> {
383    public:
384
385      typedef BAS Base;
386      typedef typename Base::Edge Edge;
387
388      using IDableDigraphComponent<Base>::id;
389
390      /// \brief Return a unique integer id for the given edge.
391      ///
392      /// This function returns a unique integer id for the given edge.
393      int id(const Edge&) const { return -1; }
394
395      /// \brief Return the edge by its unique id.
396      ///
397      /// This function returns the edge by its unique id.
398      /// If the graph does not contain an edge with the given id,
399      /// then the result of the function is undefined.
400      Edge edgeFromId(int) const { return INVALID; }
401
402      /// \brief Return an integer greater or equal to the maximum
403      /// edge id.
404      ///
405      /// This function returns an integer greater or equal to the
406      /// maximum edge id.
407      int maxEdgeId() const { return -1; }
408
409      template <typename _Graph>
410      struct Constraints {
411
412        void constraints() {
413          checkConcept<IDableDigraphComponent<Base>, _Graph >();
414          typename _Graph::Edge edge;
415          int ueid = graph.id(edge);
416          ueid = graph.id(edge);
417          edge = graph.edgeFromId(ueid);
418          ueid = graph.maxEdgeId();
419          ignore_unused_variable_warning(ueid);
420        }
421
422        const _Graph& graph;
423      };
424    };
425
426    /// \brief Concept class for \c NodeIt, \c ArcIt and \c EdgeIt types.
427    ///
428    /// This class describes the concept of \c NodeIt, \c ArcIt and
429    /// \c EdgeIt subtypes of digraph and graph types.
430    template <typename GR, typename Item>
431    class GraphItemIt : public Item {
432    public:
433      /// \brief Default constructor.
434      ///
435      /// Default constructor.
436      /// \warning The default constructor is not required to set
437      /// the iterator to some well-defined value. So you should consider it
438      /// as uninitialized.
439      GraphItemIt() {}
440
441      /// \brief Copy constructor.
442      ///
443      /// Copy constructor.
444      GraphItemIt(const GraphItemIt& it) : Item(it) {}
445
446      /// \brief Constructor that sets the iterator to the first item.
447      ///
448      /// Constructor that sets the iterator to the first item.
449      explicit GraphItemIt(const GR&) {}
450
451      /// \brief Constructor for conversion from \c INVALID.
452      ///
453      /// Constructor for conversion from \c INVALID.
454      /// It initializes the iterator to be invalid.
455      /// \sa Invalid for more details.
456      GraphItemIt(Invalid) {}
457
458      /// \brief Assignment operator.
459      ///
460      /// Assignment operator for the iterator.
461      GraphItemIt& operator=(const GraphItemIt&) { return *this; }
462
463      /// \brief Increment the iterator.
464      ///
465      /// This operator increments the iterator, i.e. assigns it to the
466      /// next item.
467      GraphItemIt& operator++() { return *this; }
468 
469      /// \brief Equality operator
470      ///
471      /// Equality operator.
472      /// Two iterators are equal if and only if they point to the
473      /// same object or both are invalid.
474      bool operator==(const GraphItemIt&) const { return true;}
475
476      /// \brief Inequality operator
477      ///
478      /// Inequality operator.
479      /// Two iterators are equal if and only if they point to the
480      /// same object or both are invalid.
481      bool operator!=(const GraphItemIt&) const { return true;}
482
483      template<typename _GraphItemIt>
484      struct Constraints {
485        void constraints() {
486          checkConcept<GraphItem<>, _GraphItemIt>();
487          _GraphItemIt it1(g);
488          _GraphItemIt it2;
489          _GraphItemIt it3 = it1;
490          _GraphItemIt it4 = INVALID;
491
492          it2 = ++it1;
493          ++it2 = it1;
494          ++(++it1);
495
496          Item bi = it1;
497          bi = it2;
498        }
499        const GR& g;
500      };
501    };
502
503    /// \brief Concept class for \c InArcIt, \c OutArcIt and
504    /// \c IncEdgeIt types.
505    ///
506    /// This class describes the concept of \c InArcIt, \c OutArcIt
507    /// and \c IncEdgeIt subtypes of digraph and graph types.
508    ///
509    /// \note Since these iterator classes do not inherit from the same
510    /// base class, there is an additional template parameter (selector)
511    /// \c sel. For \c InArcIt you should instantiate it with character
512    /// \c 'i', for \c OutArcIt with \c 'o' and for \c IncEdgeIt with \c 'e'.
513    template <typename GR,
514              typename Item = typename GR::Arc,
515              typename Base = typename GR::Node,
516              char sel = '0'>
517    class GraphIncIt : public Item {
518    public:
519      /// \brief Default constructor.
520      ///
521      /// Default constructor.
522      /// \warning The default constructor is not required to set
523      /// the iterator to some well-defined value. So you should consider it
524      /// as uninitialized.
525      GraphIncIt() {}
526
527      /// \brief Copy constructor.
528      ///
529      /// Copy constructor.
530      GraphIncIt(const GraphIncIt& it) : Item(it) {}
531
532      /// \brief Constructor that sets the iterator to the first
533      /// incoming or outgoing arc.
534      ///
535      /// Constructor that sets the iterator to the first arc
536      /// incoming to or outgoing from the given node.
537      explicit GraphIncIt(const GR&, const Base&) {}
538
539      /// \brief Constructor for conversion from \c INVALID.
540      ///
541      /// Constructor for conversion from \c INVALID.
542      /// It initializes the iterator to be invalid.
543      /// \sa Invalid for more details.
544      GraphIncIt(Invalid) {}
545
546      /// \brief Assignment operator.
547      ///
548      /// Assignment operator for the iterator.
549      GraphIncIt& operator=(const GraphIncIt&) { return *this; }
550
551      /// \brief Increment the iterator.
552      ///
553      /// This operator increments the iterator, i.e. assigns it to the
554      /// next arc incoming to or outgoing from the given node.
555      GraphIncIt& operator++() { return *this; }
556
557      /// \brief Equality operator
558      ///
559      /// Equality operator.
560      /// Two iterators are equal if and only if they point to the
561      /// same object or both are invalid.
562      bool operator==(const GraphIncIt&) const { return true;}
563
564      /// \brief Inequality operator
565      ///
566      /// Inequality operator.
567      /// Two iterators are equal if and only if they point to the
568      /// same object or both are invalid.
569      bool operator!=(const GraphIncIt&) const { return true;}
570
571      template <typename _GraphIncIt>
572      struct Constraints {
573        void constraints() {
574          checkConcept<GraphItem<sel>, _GraphIncIt>();
575          _GraphIncIt it1(graph, node);
576          _GraphIncIt it2;
577          _GraphIncIt it3 = it1;
578          _GraphIncIt it4 = INVALID;
579
580          it2 = ++it1;
581          ++it2 = it1;
582          ++(++it1);
583          Item e = it1;
584          e = it2;
585        }
586        const Base& node;
587        const GR& graph;
588      };
589    };
590
591    /// \brief Skeleton class for iterable directed graphs.
592    ///
593    /// This class describes the interface of iterable directed
594    /// graphs. It extends \ref BaseDigraphComponent with the core
595    /// iterable interface.
596    /// This concept is part of the Digraph concept.
597    template <typename BAS = BaseDigraphComponent>
598    class IterableDigraphComponent : public BAS {
599
600    public:
601
602      typedef BAS Base;
603      typedef typename Base::Node Node;
604      typedef typename Base::Arc Arc;
605
606      typedef IterableDigraphComponent Digraph;
607
608      /// \name Base Iteration
609      ///
610      /// This interface provides functions for iteration on digraph items.
611      ///
612      /// @{
613
614      /// \brief Return the first node.
615      ///
616      /// This function gives back the first node in the iteration order.
617      void first(Node&) const {}
618
619      /// \brief Return the next node.
620      ///
621      /// This function gives back the next node in the iteration order.
622      void next(Node&) const {}
623
624      /// \brief Return the first arc.
625      ///
626      /// This function gives back the first arc in the iteration order.
627      void first(Arc&) const {}
628
629      /// \brief Return the next arc.
630      ///
631      /// This function gives back the next arc in the iteration order.
632      void next(Arc&) const {}
633
634      /// \brief Return the first arc incomming to the given node.
635      ///
636      /// This function gives back the first arc incomming to the
637      /// given node.
638      void firstIn(Arc&, const Node&) const {}
639
640      /// \brief Return the next arc incomming to the given node.
641      ///
642      /// This function gives back the next arc incomming to the
643      /// given node.
644      void nextIn(Arc&) const {}
645
646      /// \brief Return the first arc outgoing form the given node.
647      ///
648      /// This function gives back the first arc outgoing form the
649      /// given node.
650      void firstOut(Arc&, const Node&) const {}
651
652      /// \brief Return the next arc outgoing form the given node.
653      ///
654      /// This function gives back the next arc outgoing form the
655      /// given node.
656      void nextOut(Arc&) const {}
657
658      /// @}
659
660      /// \name Class Based Iteration
661      ///
662      /// This interface provides iterator classes for digraph items.
663      ///
664      /// @{
665
666      /// \brief This iterator goes through each node.
667      ///
668      /// This iterator goes through each node.
669      ///
670      typedef GraphItemIt<Digraph, Node> NodeIt;
671
672      /// \brief This iterator goes through each arc.
673      ///
674      /// This iterator goes through each arc.
675      ///
676      typedef GraphItemIt<Digraph, Arc> ArcIt;
677
678      /// \brief This iterator goes trough the incoming arcs of a node.
679      ///
680      /// This iterator goes trough the \e incoming arcs of a certain node
681      /// of a digraph.
682      typedef GraphIncIt<Digraph, Arc, Node, 'i'> InArcIt;
683
684      /// \brief This iterator goes trough the outgoing arcs of a node.
685      ///
686      /// This iterator goes trough the \e outgoing arcs of a certain node
687      /// of a digraph.
688      typedef GraphIncIt<Digraph, Arc, Node, 'o'> OutArcIt;
689
690      /// \brief The base node of the iterator.
691      ///
692      /// This function gives back the base node of the iterator.
693      /// It is always the target node of the pointed arc.
694      Node baseNode(const InArcIt&) const { return INVALID; }
695
696      /// \brief The running node of the iterator.
697      ///
698      /// This function gives back the running node of the iterator.
699      /// It is always the source node of the pointed arc.
700      Node runningNode(const InArcIt&) const { return INVALID; }
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 source node of the pointed arc.
706      Node baseNode(const OutArcIt&) 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 target node of the pointed arc.
712      Node runningNode(const OutArcIt&) const { return INVALID; }
713
714      /// @}
715
716      template <typename _Digraph>
717      struct Constraints {
718        void constraints() {
719          checkConcept<Base, _Digraph>();
720
721          {
722            typename _Digraph::Node node(INVALID);
723            typename _Digraph::Arc arc(INVALID);
724            {
725              digraph.first(node);
726              digraph.next(node);
727            }
728            {
729              digraph.first(arc);
730              digraph.next(arc);
731            }
732            {
733              digraph.firstIn(arc, node);
734              digraph.nextIn(arc);
735            }
736            {
737              digraph.firstOut(arc, node);
738              digraph.nextOut(arc);
739            }
740          }
741
742          {
743            checkConcept<GraphItemIt<_Digraph, typename _Digraph::Arc>,
744              typename _Digraph::ArcIt >();
745            checkConcept<GraphItemIt<_Digraph, typename _Digraph::Node>,
746              typename _Digraph::NodeIt >();
747            checkConcept<GraphIncIt<_Digraph, typename _Digraph::Arc,
748              typename _Digraph::Node, 'i'>, typename _Digraph::InArcIt>();
749            checkConcept<GraphIncIt<_Digraph, typename _Digraph::Arc,
750              typename _Digraph::Node, 'o'>, typename _Digraph::OutArcIt>();
751
752            typename _Digraph::Node n;
753            const typename _Digraph::InArcIt iait(INVALID);
754            const typename _Digraph::OutArcIt oait(INVALID);
755            n = digraph.baseNode(iait);
756            n = digraph.runningNode(iait);
757            n = digraph.baseNode(oait);
758            n = digraph.runningNode(oait);
759            ignore_unused_variable_warning(n);
760          }
761        }
762
763        const _Digraph& digraph;
764      };
765    };
766
767    /// \brief Skeleton class for iterable undirected graphs.
768    ///
769    /// This class describes the interface of iterable undirected
770    /// graphs. It extends \ref IterableDigraphComponent with the core
771    /// iterable interface of undirected graphs.
772    /// This concept is part of the Graph concept.
773    template <typename BAS = BaseGraphComponent>
774    class IterableGraphComponent : public IterableDigraphComponent<BAS> {
775    public:
776
777      typedef BAS Base;
778      typedef typename Base::Node Node;
779      typedef typename Base::Arc Arc;
780      typedef typename Base::Edge Edge;
781
782
783      typedef IterableGraphComponent Graph;
784
785      /// \name Base Iteration
786      ///
787      /// This interface provides functions for iteration on edges.
788      ///
789      /// @{
790
791      using IterableDigraphComponent<Base>::first;
792      using IterableDigraphComponent<Base>::next;
793
794      /// \brief Return the first edge.
795      ///
796      /// This function gives back the first edge in the iteration order.
797      void first(Edge&) const {}
798
799      /// \brief Return the next edge.
800      ///
801      /// This function gives back the next edge in the iteration order.
802      void next(Edge&) const {}
803
804      /// \brief Return the first edge incident to the given node.
805      ///
806      /// This function gives back the first edge incident to the given
807      /// node. The bool parameter gives back the direction for which the
808      /// source node of the directed arc representing the edge is the
809      /// given node.
810      void firstInc(Edge&, bool&, const Node&) const {}
811
812      /// \brief Gives back the next of the edges from the
813      /// given node.
814      ///
815      /// This function gives back the next edge incident to the given
816      /// node. The bool parameter should be used as \c firstInc() use it.
817      void nextInc(Edge&, bool&) const {}
818
819      using IterableDigraphComponent<Base>::baseNode;
820      using IterableDigraphComponent<Base>::runningNode;
821
822      /// @}
823
824      /// \name Class Based Iteration
825      ///
826      /// This interface provides iterator classes for edges.
827      ///
828      /// @{
829
830      /// \brief This iterator goes through each edge.
831      ///
832      /// This iterator goes through each edge.
833      typedef GraphItemIt<Graph, Edge> EdgeIt;
834
835      /// \brief This iterator goes trough the incident edges of a
836      /// node.
837      ///
838      /// This iterator goes trough the incident edges of a certain
839      /// node of a graph.
840      typedef GraphIncIt<Graph, Edge, Node, 'e'> IncEdgeIt;
841
842      /// \brief The base node of the iterator.
843      ///
844      /// This function gives back the base node of the iterator.
845      Node baseNode(const IncEdgeIt&) const { return INVALID; }
846
847      /// \brief The running node of the iterator.
848      ///
849      /// This function gives back the running node of the iterator.
850      Node runningNode(const IncEdgeIt&) const { return INVALID; }
851
852      /// @}
853
854      template <typename _Graph>
855      struct Constraints {
856        void constraints() {
857          checkConcept<IterableDigraphComponent<Base>, _Graph>();
858
859          {
860            typename _Graph::Node node(INVALID);
861            typename _Graph::Edge edge(INVALID);
862            bool dir;
863            {
864              graph.first(edge);
865              graph.next(edge);
866            }
867            {
868              graph.firstInc(edge, dir, node);
869              graph.nextInc(edge, dir);
870            }
871
872          }
873
874          {
875            checkConcept<GraphItemIt<_Graph, typename _Graph::Edge>,
876              typename _Graph::EdgeIt >();
877            checkConcept<GraphIncIt<_Graph, typename _Graph::Edge,
878              typename _Graph::Node, 'e'>, typename _Graph::IncEdgeIt>();
879
880            typename _Graph::Node n;
881            const typename _Graph::IncEdgeIt ieit(INVALID);
882            n = graph.baseNode(ieit);
883            n = graph.runningNode(ieit);
884          }
885        }
886
887        const _Graph& graph;
888      };
889    };
890
891    /// \brief Skeleton class for alterable directed graphs.
892    ///
893    /// This class describes the interface of alterable directed
894    /// graphs. It extends \ref BaseDigraphComponent with the alteration
895    /// notifier interface. It implements
896    /// an observer-notifier pattern for each digraph item. More
897    /// obsevers can be registered into the notifier and whenever an
898    /// alteration occured in the digraph all the observers will be
899    /// notified about it.
900    template <typename BAS = BaseDigraphComponent>
901    class AlterableDigraphComponent : public BAS {
902    public:
903
904      typedef BAS Base;
905      typedef typename Base::Node Node;
906      typedef typename Base::Arc Arc;
907
908
909      /// Node alteration notifier class.
910      typedef AlterationNotifier<AlterableDigraphComponent, Node>
911      NodeNotifier;
912      /// Arc alteration notifier class.
913      typedef AlterationNotifier<AlterableDigraphComponent, Arc>
914      ArcNotifier;
915
916      /// \brief Return the node alteration notifier.
917      ///
918      /// This function gives back the node alteration notifier.
919      NodeNotifier& notifier(Node) const {
920         return NodeNotifier();
921      }
922
923      /// \brief Return the arc alteration notifier.
924      ///
925      /// This function gives back the arc alteration notifier.
926      ArcNotifier& notifier(Arc) const {
927        return ArcNotifier();
928      }
929
930      template <typename _Digraph>
931      struct Constraints {
932        void constraints() {
933          checkConcept<Base, _Digraph>();
934          typename _Digraph::NodeNotifier& nn
935            = digraph.notifier(typename _Digraph::Node());
936
937          typename _Digraph::ArcNotifier& en
938            = digraph.notifier(typename _Digraph::Arc());
939
940          ignore_unused_variable_warning(nn);
941          ignore_unused_variable_warning(en);
942        }
943
944        const _Digraph& digraph;
945      };
946    };
947
948    /// \brief Skeleton class for alterable undirected graphs.
949    ///
950    /// This class describes the interface of alterable undirected
951    /// graphs. It extends \ref AlterableDigraphComponent with the alteration
952    /// notifier interface of undirected graphs. It implements
953    /// an observer-notifier pattern for the edges. More
954    /// obsevers can be registered into the notifier and whenever an
955    /// alteration occured in the graph all the observers will be
956    /// notified about it.
957    template <typename BAS = BaseGraphComponent>
958    class AlterableGraphComponent : public AlterableDigraphComponent<BAS> {
959    public:
960
961      typedef BAS Base;
962      typedef typename Base::Edge Edge;
963
964
965      /// Edge alteration notifier class.
966      typedef AlterationNotifier<AlterableGraphComponent, Edge>
967      EdgeNotifier;
968
969      /// \brief Return the edge alteration notifier.
970      ///
971      /// This function gives back the edge alteration notifier.
972      EdgeNotifier& notifier(Edge) const {
973        return EdgeNotifier();
974      }
975
976      template <typename _Graph>
977      struct Constraints {
978        void constraints() {
979          checkConcept<AlterableDigraphComponent<Base>, _Graph>();
980          typename _Graph::EdgeNotifier& uen
981            = graph.notifier(typename _Graph::Edge());
982          ignore_unused_variable_warning(uen);
983        }
984
985        const _Graph& graph;
986      };
987    };
988
989    /// \brief Concept class for standard graph maps.
990    ///
991    /// This class describes the concept of standard graph maps, i.e.
992    /// the \c NodeMap, \c ArcMap and \c EdgeMap subtypes of digraph and
993    /// graph types, which can be used for associating data to graph items.
994    /// The standard graph maps must conform to the ReferenceMap concept.
995    template <typename GR, typename K, typename V>
996    class GraphMap : public ReferenceMap<K, V, V&, const V&> {
997      typedef ReferenceMap<K, V, V&, const V&> Parent;
998
999    public:
1000
1001      /// The key type of the map.
1002      typedef K Key;
1003      /// The value type of the map.
1004      typedef V Value;
1005      /// The reference type of the map.
1006      typedef Value& Reference;
1007      /// The const reference type of the map.
1008      typedef const Value& ConstReference;
1009
1010      // The reference map tag.
1011      typedef True ReferenceMapTag;
1012
1013      /// \brief Construct a new map.
1014      ///
1015      /// Construct a new map for the graph.
1016      explicit GraphMap(const GR&) {}
1017      /// \brief Construct a new map with default value.
1018      ///
1019      /// Construct a new map for the graph and initalize the values.
1020      GraphMap(const GR&, const Value&) {}
1021
1022    private:
1023      /// \brief Copy constructor.
1024      ///
1025      /// Copy Constructor.
1026      GraphMap(const GraphMap&) : Parent() {}
1027
1028      /// \brief Assignment operator.
1029      ///
1030      /// Assignment operator. It does not mofify the underlying graph,
1031      /// it just iterates on the current item set and set the  map
1032      /// with the value returned by the assigned map.
1033      template <typename CMap>
1034      GraphMap& operator=(const CMap&) {
1035        checkConcept<ReadMap<Key, Value>, CMap>();
1036        return *this;
1037      }
1038
1039    public:
1040      template<typename _Map>
1041      struct Constraints {
1042        void constraints() {
1043          checkConcept
1044            <ReferenceMap<Key, Value, Value&, const Value&>, _Map>();
1045          _Map m1(g);
1046          _Map m2(g,t);
1047         
1048          // Copy constructor
1049          // _Map m3(m);
1050
1051          // Assignment operator
1052          // ReadMap<Key, Value> cmap;
1053          // m3 = cmap;
1054
1055          ignore_unused_variable_warning(m1);
1056          ignore_unused_variable_warning(m2);
1057          // ignore_unused_variable_warning(m3);
1058        }
1059
1060        const _Map &m;
1061        const GR &g;
1062        const typename GraphMap::Value &t;
1063      };
1064
1065    };
1066
1067    /// \brief Skeleton class for mappable directed graphs.
1068    ///
1069    /// This class describes the interface of mappable directed graphs.
1070    /// It extends \ref BaseDigraphComponent with the standard digraph
1071    /// map classes, namely \c NodeMap and \c ArcMap.
1072    /// This concept is part of the Digraph concept.
1073    template <typename BAS = BaseDigraphComponent>
1074    class MappableDigraphComponent : public BAS  {
1075    public:
1076
1077      typedef BAS Base;
1078      typedef typename Base::Node Node;
1079      typedef typename Base::Arc Arc;
1080
1081      typedef MappableDigraphComponent Digraph;
1082
1083      /// \brief Standard graph map for the nodes.
1084      ///
1085      /// Standard graph map for the nodes.
1086      /// It conforms to the ReferenceMap concept.
1087      template <typename V>
1088      class NodeMap : public GraphMap<MappableDigraphComponent, Node, V> {
1089        typedef GraphMap<MappableDigraphComponent, Node, V> Parent;
1090
1091      public:
1092        /// \brief Construct a new map.
1093        ///
1094        /// Construct a new map for the digraph.
1095        explicit NodeMap(const MappableDigraphComponent& digraph)
1096          : Parent(digraph) {}
1097
1098        /// \brief Construct a new map with default value.
1099        ///
1100        /// Construct a new map for the digraph and initalize the values.
1101        NodeMap(const MappableDigraphComponent& digraph, const V& value)
1102          : Parent(digraph, value) {}
1103
1104      private:
1105        /// \brief Copy constructor.
1106        ///
1107        /// Copy Constructor.
1108        NodeMap(const NodeMap& nm) : Parent(nm) {}
1109
1110        /// \brief Assignment operator.
1111        ///
1112        /// Assignment operator.
1113        template <typename CMap>
1114        NodeMap& operator=(const CMap&) {
1115          checkConcept<ReadMap<Node, V>, CMap>();
1116          return *this;
1117        }
1118
1119      };
1120
1121      /// \brief Standard graph map for the arcs.
1122      ///
1123      /// Standard graph map for the arcs.
1124      /// It conforms to the ReferenceMap concept.
1125      template <typename V>
1126      class ArcMap : public GraphMap<MappableDigraphComponent, Arc, V> {
1127        typedef GraphMap<MappableDigraphComponent, Arc, V> Parent;
1128
1129      public:
1130        /// \brief Construct a new map.
1131        ///
1132        /// Construct a new map for the digraph.
1133        explicit ArcMap(const MappableDigraphComponent& digraph)
1134          : Parent(digraph) {}
1135
1136        /// \brief Construct a new map with default value.
1137        ///
1138        /// Construct a new map for the digraph and initalize the values.
1139        ArcMap(const MappableDigraphComponent& digraph, const V& value)
1140          : Parent(digraph, value) {}
1141
1142      private:
1143        /// \brief Copy constructor.
1144        ///
1145        /// Copy Constructor.
1146        ArcMap(const ArcMap& nm) : Parent(nm) {}
1147
1148        /// \brief Assignment operator.
1149        ///
1150        /// Assignment operator.
1151        template <typename CMap>
1152        ArcMap& operator=(const CMap&) {
1153          checkConcept<ReadMap<Arc, V>, CMap>();
1154          return *this;
1155        }
1156
1157      };
1158
1159
1160      template <typename _Digraph>
1161      struct Constraints {
1162
1163        struct Dummy {
1164          int value;
1165          Dummy() : value(0) {}
1166          Dummy(int _v) : value(_v) {}
1167        };
1168
1169        void constraints() {
1170          checkConcept<Base, _Digraph>();
1171          { // int map test
1172            typedef typename _Digraph::template NodeMap<int> IntNodeMap;
1173            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, int>,
1174              IntNodeMap >();
1175          } { // bool map test
1176            typedef typename _Digraph::template NodeMap<bool> BoolNodeMap;
1177            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, bool>,
1178              BoolNodeMap >();
1179          } { // Dummy map test
1180            typedef typename _Digraph::template NodeMap<Dummy> DummyNodeMap;
1181            checkConcept<GraphMap<_Digraph, typename _Digraph::Node, Dummy>,
1182              DummyNodeMap >();
1183          }
1184
1185          { // int map test
1186            typedef typename _Digraph::template ArcMap<int> IntArcMap;
1187            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, int>,
1188              IntArcMap >();
1189          } { // bool map test
1190            typedef typename _Digraph::template ArcMap<bool> BoolArcMap;
1191            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, bool>,
1192              BoolArcMap >();
1193          } { // Dummy map test
1194            typedef typename _Digraph::template ArcMap<Dummy> DummyArcMap;
1195            checkConcept<GraphMap<_Digraph, typename _Digraph::Arc, Dummy>,
1196              DummyArcMap >();
1197          }
1198        }
1199
1200        const _Digraph& digraph;
1201      };
1202    };
1203
1204    /// \brief Skeleton class for mappable undirected graphs.
1205    ///
1206    /// This class describes the interface of mappable undirected graphs.
1207    /// It extends \ref MappableDigraphComponent with the standard graph
1208    /// map class for edges (\c EdgeMap).
1209    /// This concept is part of the Graph concept.
1210    template <typename BAS = BaseGraphComponent>
1211    class MappableGraphComponent : public MappableDigraphComponent<BAS>  {
1212    public:
1213
1214      typedef BAS Base;
1215      typedef typename Base::Edge Edge;
1216
1217      typedef MappableGraphComponent Graph;
1218
1219      /// \brief Standard graph map for the edges.
1220      ///
1221      /// Standard graph map for the edges.
1222      /// It conforms to the ReferenceMap concept.
1223      template <typename V>
1224      class EdgeMap : public GraphMap<MappableGraphComponent, Edge, V> {
1225        typedef GraphMap<MappableGraphComponent, Edge, V> Parent;
1226
1227      public:
1228        /// \brief Construct a new map.
1229        ///
1230        /// Construct a new map for the graph.
1231        explicit EdgeMap(const MappableGraphComponent& graph)
1232          : Parent(graph) {}
1233
1234        /// \brief Construct a new map with default value.
1235        ///
1236        /// Construct a new map for the graph and initalize the values.
1237        EdgeMap(const MappableGraphComponent& graph, const V& value)
1238          : Parent(graph, value) {}
1239
1240      private:
1241        /// \brief Copy constructor.
1242        ///
1243        /// Copy Constructor.
1244        EdgeMap(const EdgeMap& nm) : Parent(nm) {}
1245
1246        /// \brief Assignment operator.
1247        ///
1248        /// Assignment operator.
1249        template <typename CMap>
1250        EdgeMap& operator=(const CMap&) {
1251          checkConcept<ReadMap<Edge, V>, CMap>();
1252          return *this;
1253        }
1254
1255      };
1256
1257
1258      template <typename _Graph>
1259      struct Constraints {
1260
1261        struct Dummy {
1262          int value;
1263          Dummy() : value(0) {}
1264          Dummy(int _v) : value(_v) {}
1265        };
1266
1267        void constraints() {
1268          checkConcept<MappableDigraphComponent<Base>, _Graph>();
1269
1270          { // int map test
1271            typedef typename _Graph::template EdgeMap<int> IntEdgeMap;
1272            checkConcept<GraphMap<_Graph, typename _Graph::Edge, int>,
1273              IntEdgeMap >();
1274          } { // bool map test
1275            typedef typename _Graph::template EdgeMap<bool> BoolEdgeMap;
1276            checkConcept<GraphMap<_Graph, typename _Graph::Edge, bool>,
1277              BoolEdgeMap >();
1278          } { // Dummy map test
1279            typedef typename _Graph::template EdgeMap<Dummy> DummyEdgeMap;
1280            checkConcept<GraphMap<_Graph, typename _Graph::Edge, Dummy>,
1281              DummyEdgeMap >();
1282          }
1283        }
1284
1285        const _Graph& graph;
1286      };
1287    };
1288
1289    /// \brief Skeleton class for extendable directed graphs.
1290    ///
1291    /// This class describes the interface of extendable directed graphs.
1292    /// It extends \ref BaseDigraphComponent with functions for adding
1293    /// nodes and arcs to the digraph.
1294    /// This concept requires \ref AlterableDigraphComponent.
1295    template <typename BAS = BaseDigraphComponent>
1296    class ExtendableDigraphComponent : public BAS {
1297    public:
1298      typedef BAS Base;
1299
1300      typedef typename Base::Node Node;
1301      typedef typename Base::Arc Arc;
1302
1303      /// \brief Add a new node to the digraph.
1304      ///
1305      /// This function adds a new node to the digraph.
1306      Node addNode() {
1307        return INVALID;
1308      }
1309
1310      /// \brief Add a new arc connecting the given two nodes.
1311      ///
1312      /// This function adds a new arc connecting the given two nodes
1313      /// of the digraph.
1314      Arc addArc(const Node&, const Node&) {
1315        return INVALID;
1316      }
1317
1318      template <typename _Digraph>
1319      struct Constraints {
1320        void constraints() {
1321          checkConcept<Base, _Digraph>();
1322          typename _Digraph::Node node_a, node_b;
1323          node_a = digraph.addNode();
1324          node_b = digraph.addNode();
1325          typename _Digraph::Arc arc;
1326          arc = digraph.addArc(node_a, node_b);
1327        }
1328
1329        _Digraph& digraph;
1330      };
1331    };
1332
1333    /// \brief Skeleton class for extendable undirected graphs.
1334    ///
1335    /// This class describes the interface of extendable undirected graphs.
1336    /// It extends \ref BaseGraphComponent with functions for adding
1337    /// nodes and edges to the graph.
1338    /// This concept requires \ref AlterableGraphComponent.
1339    template <typename BAS = BaseGraphComponent>
1340    class ExtendableGraphComponent : public BAS {
1341    public:
1342
1343      typedef BAS Base;
1344      typedef typename Base::Node Node;
1345      typedef typename Base::Edge Edge;
1346
1347      /// \brief Add a new node to the digraph.
1348      ///
1349      /// This function adds a new node to the digraph.
1350      Node addNode() {
1351        return INVALID;
1352      }
1353
1354      /// \brief Add a new edge connecting the given two nodes.
1355      ///
1356      /// This function adds a new edge connecting the given two nodes
1357      /// of the graph.
1358      Edge addEdge(const Node&, const Node&) {
1359        return INVALID;
1360      }
1361
1362      template <typename _Graph>
1363      struct Constraints {
1364        void constraints() {
1365          checkConcept<Base, _Graph>();
1366          typename _Graph::Node node_a, node_b;
1367          node_a = graph.addNode();
1368          node_b = graph.addNode();
1369          typename _Graph::Edge edge;
1370          edge = graph.addEdge(node_a, node_b);
1371        }
1372
1373        _Graph& graph;
1374      };
1375    };
1376
1377    /// \brief Skeleton class for erasable directed graphs.
1378    ///
1379    /// This class describes the interface of erasable directed graphs.
1380    /// It extends \ref BaseDigraphComponent with functions for removing
1381    /// nodes and arcs from the digraph.
1382    /// This concept requires \ref AlterableDigraphComponent.
1383    template <typename BAS = BaseDigraphComponent>
1384    class ErasableDigraphComponent : public BAS {
1385    public:
1386
1387      typedef BAS Base;
1388      typedef typename Base::Node Node;
1389      typedef typename Base::Arc Arc;
1390
1391      /// \brief Erase a node from the digraph.
1392      ///
1393      /// This function erases the given node from the digraph and all arcs
1394      /// connected to the node.
1395      void erase(const Node&) {}
1396
1397      /// \brief Erase an arc from the digraph.
1398      ///
1399      /// This function erases the given arc from the digraph.
1400      void erase(const Arc&) {}
1401
1402      template <typename _Digraph>
1403      struct Constraints {
1404        void constraints() {
1405          checkConcept<Base, _Digraph>();
1406          const typename _Digraph::Node node(INVALID);
1407          digraph.erase(node);
1408          const typename _Digraph::Arc arc(INVALID);
1409          digraph.erase(arc);
1410        }
1411
1412        _Digraph& digraph;
1413      };
1414    };
1415
1416    /// \brief Skeleton class for erasable undirected graphs.
1417    ///
1418    /// This class describes the interface of erasable undirected graphs.
1419    /// It extends \ref BaseGraphComponent with functions for removing
1420    /// nodes and edges from the graph.
1421    /// This concept requires \ref AlterableGraphComponent.
1422    template <typename BAS = BaseGraphComponent>
1423    class ErasableGraphComponent : public BAS {
1424    public:
1425
1426      typedef BAS Base;
1427      typedef typename Base::Node Node;
1428      typedef typename Base::Edge Edge;
1429
1430      /// \brief Erase a node from the graph.
1431      ///
1432      /// This function erases the given node from the graph and all edges
1433      /// connected to the node.
1434      void erase(const Node&) {}
1435
1436      /// \brief Erase an edge from the digraph.
1437      ///
1438      /// This function erases the given edge from the digraph.
1439      void erase(const Edge&) {}
1440
1441      template <typename _Graph>
1442      struct Constraints {
1443        void constraints() {
1444          checkConcept<Base, _Graph>();
1445          const typename _Graph::Node node(INVALID);
1446          graph.erase(node);
1447          const typename _Graph::Edge edge(INVALID);
1448          graph.erase(edge);
1449        }
1450
1451        _Graph& graph;
1452      };
1453    };
1454
1455    /// \brief Skeleton class for clearable directed graphs.
1456    ///
1457    /// This class describes the interface of clearable directed graphs.
1458    /// It extends \ref BaseDigraphComponent with a function for clearing
1459    /// the digraph.
1460    /// This concept requires \ref AlterableDigraphComponent.
1461    template <typename BAS = BaseDigraphComponent>
1462    class ClearableDigraphComponent : public BAS {
1463    public:
1464
1465      typedef BAS Base;
1466
1467      /// \brief Erase all nodes and arcs from the digraph.
1468      ///
1469      /// This function erases all nodes and arcs from the digraph.
1470      void clear() {}
1471
1472      template <typename _Digraph>
1473      struct Constraints {
1474        void constraints() {
1475          checkConcept<Base, _Digraph>();
1476          digraph.clear();
1477        }
1478
1479        _Digraph& digraph;
1480      };
1481    };
1482
1483    /// \brief Skeleton class for clearable undirected graphs.
1484    ///
1485    /// This class describes the interface of clearable undirected graphs.
1486    /// It extends \ref BaseGraphComponent with a function for clearing
1487    /// the graph.
1488    /// This concept requires \ref AlterableGraphComponent.
1489    template <typename BAS = BaseGraphComponent>
1490    class ClearableGraphComponent : public ClearableDigraphComponent<BAS> {
1491    public:
1492
1493      typedef BAS Base;
1494
1495      /// \brief Erase all nodes and edges from the graph.
1496      ///
1497      /// This function erases all nodes and edges from the graph.
1498      void clear() {}
1499
1500      template <typename _Graph>
1501      struct Constraints {
1502        void constraints() {
1503          checkConcept<Base, _Graph>();
1504          graph.clear();
1505        }
1506
1507        _Graph& graph;
1508      };
1509    };
1510
1511  }
1512
1513}
1514
1515#endif
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