lemon/concepts/digraph.h
changeset 964 2b6bffe0e7e8
parent 786 e20173729589
child 1049 7bf489cf624e
child 1084 8b2d4e5d96e4
     1.1 --- a/lemon/concepts/digraph.h	Tue Dec 20 17:44:38 2011 +0100
     1.2 +++ b/lemon/concepts/digraph.h	Tue Dec 20 18:15:14 2011 +0100
     1.3 @@ -2,7 +2,7 @@
     1.4   *
     1.5   * This file is a part of LEMON, a generic C++ optimization library.
     1.6   *
     1.7 - * Copyright (C) 2003-2009
     1.8 + * Copyright (C) 2003-2010
     1.9   * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
    1.10   * (Egervary Research Group on Combinatorial Optimization, EGRES).
    1.11   *
    1.12 @@ -35,46 +35,40 @@
    1.13      ///
    1.14      /// \brief Class describing the concept of directed graphs.
    1.15      ///
    1.16 -    /// This class describes the \ref concept "concept" of the
    1.17 -    /// immutable directed digraphs.
    1.18 +    /// This class describes the common interface of all directed
    1.19 +    /// graphs (digraphs).
    1.20      ///
    1.21 -    /// Note that actual digraph implementation like @ref ListDigraph or
    1.22 -    /// @ref SmartDigraph may have several additional functionality.
    1.23 +    /// Like all concept classes, it only provides an interface
    1.24 +    /// without any sensible implementation. So any general algorithm for
    1.25 +    /// directed graphs should compile with this class, but it will not
    1.26 +    /// run properly, of course.
    1.27 +    /// An actual digraph implementation like \ref ListDigraph or
    1.28 +    /// \ref SmartDigraph may have additional functionality.
    1.29      ///
    1.30 -    /// \sa concept
    1.31 +    /// \sa Graph
    1.32      class Digraph {
    1.33      private:
    1.34 -      ///Digraphs are \e not copy constructible. Use DigraphCopy() instead.
    1.35 +      /// Diraphs are \e not copy constructible. Use DigraphCopy instead.
    1.36 +      Digraph(const Digraph &) {}
    1.37 +      /// \brief Assignment of a digraph to another one is \e not allowed.
    1.38 +      /// Use DigraphCopy instead.
    1.39 +      void operator=(const Digraph &) {}
    1.40  
    1.41 -      ///Digraphs are \e not copy constructible. Use DigraphCopy() instead.
    1.42 -      ///
    1.43 -      Digraph(const Digraph &) {};
    1.44 -      ///\brief Assignment of \ref Digraph "Digraph"s to another ones are
    1.45 -      ///\e not allowed. Use DigraphCopy() instead.
    1.46 +    public:
    1.47 +      /// Default constructor.
    1.48 +      Digraph() { }
    1.49  
    1.50 -      ///Assignment of \ref Digraph "Digraph"s to another ones are
    1.51 -      ///\e not allowed.  Use DigraphCopy() instead.
    1.52 -
    1.53 -      void operator=(const Digraph &) {}
    1.54 -    public:
    1.55 -      ///\e
    1.56 -
    1.57 -      /// Defalult constructor.
    1.58 -
    1.59 -      /// Defalult constructor.
    1.60 -      ///
    1.61 -      Digraph() { }
    1.62 -      /// Class for identifying a node of the digraph
    1.63 +      /// The node type of the digraph
    1.64  
    1.65        /// This class identifies a node of the digraph. It also serves
    1.66        /// as a base class of the node iterators,
    1.67 -      /// thus they will convert to this type.
    1.68 +      /// thus they convert to this type.
    1.69        class Node {
    1.70        public:
    1.71          /// Default constructor
    1.72  
    1.73 -        /// @warning The default constructor sets the iterator
    1.74 -        /// to an undefined value.
    1.75 +        /// Default constructor.
    1.76 +        /// \warning It sets the object to an undefined value.
    1.77          Node() { }
    1.78          /// Copy constructor.
    1.79  
    1.80 @@ -82,40 +76,39 @@
    1.81          ///
    1.82          Node(const Node&) { }
    1.83  
    1.84 -        /// Invalid constructor \& conversion.
    1.85 +        /// %Invalid constructor \& conversion.
    1.86  
    1.87 -        /// This constructor initializes the iterator to be invalid.
    1.88 +        /// Initializes the object to be invalid.
    1.89          /// \sa Invalid for more details.
    1.90          Node(Invalid) { }
    1.91          /// Equality operator
    1.92  
    1.93 +        /// Equality operator.
    1.94 +        ///
    1.95          /// Two iterators are equal if and only if they point to the
    1.96 -        /// same object or both are invalid.
    1.97 +        /// same object or both are \c INVALID.
    1.98          bool operator==(Node) const { return true; }
    1.99  
   1.100          /// Inequality operator
   1.101  
   1.102 -        /// \sa operator==(Node n)
   1.103 -        ///
   1.104 +        /// Inequality operator.
   1.105          bool operator!=(Node) const { return true; }
   1.106  
   1.107          /// Artificial ordering operator.
   1.108  
   1.109 -        /// To allow the use of digraph descriptors as key type in std::map or
   1.110 -        /// similar associative container we require this.
   1.111 +        /// Artificial ordering operator.
   1.112          ///
   1.113 -        /// \note This operator only have to define some strict ordering of
   1.114 -        /// the items; this order has nothing to do with the iteration
   1.115 -        /// ordering of the items.
   1.116 +        /// \note This operator only has to define some strict ordering of
   1.117 +        /// the nodes; this order has nothing to do with the iteration
   1.118 +        /// ordering of the nodes.
   1.119          bool operator<(Node) const { return false; }
   1.120 -
   1.121        };
   1.122  
   1.123 -      /// This iterator goes through each node.
   1.124 +      /// Iterator class for the nodes.
   1.125  
   1.126 -      /// This iterator goes through each node.
   1.127 -      /// Its usage is quite simple, for example you can count the number
   1.128 -      /// of nodes in digraph \c g of type \c Digraph like this:
   1.129 +      /// This iterator goes through each node of the digraph.
   1.130 +      /// Its usage is quite simple, for example, you can count the number
   1.131 +      /// of nodes in a digraph \c g of type \c %Digraph like this:
   1.132        ///\code
   1.133        /// int count=0;
   1.134        /// for (Digraph::NodeIt n(g); n!=INVALID; ++n) ++count;
   1.135 @@ -124,30 +117,28 @@
   1.136        public:
   1.137          /// Default constructor
   1.138  
   1.139 -        /// @warning The default constructor sets the iterator
   1.140 -        /// to an undefined value.
   1.141 +        /// Default constructor.
   1.142 +        /// \warning It sets the iterator to an undefined value.
   1.143          NodeIt() { }
   1.144          /// Copy constructor.
   1.145  
   1.146          /// Copy constructor.
   1.147          ///
   1.148          NodeIt(const NodeIt& n) : Node(n) { }
   1.149 -        /// Invalid constructor \& conversion.
   1.150 +        /// %Invalid constructor \& conversion.
   1.151  
   1.152 -        /// Initialize the iterator to be invalid.
   1.153 +        /// Initializes the iterator to be invalid.
   1.154          /// \sa Invalid for more details.
   1.155          NodeIt(Invalid) { }
   1.156          /// Sets the iterator to the first node.
   1.157  
   1.158 -        /// Sets the iterator to the first node of \c g.
   1.159 +        /// Sets the iterator to the first node of the given digraph.
   1.160          ///
   1.161 -        NodeIt(const Digraph&) { }
   1.162 -        /// Node -> NodeIt conversion.
   1.163 +        explicit NodeIt(const Digraph&) { }
   1.164 +        /// Sets the iterator to the given node.
   1.165  
   1.166 -        /// Sets the iterator to the node of \c the digraph pointed by
   1.167 -        /// the trivial iterator.
   1.168 -        /// This feature necessitates that each time we
   1.169 -        /// iterate the arc-set, the iteration order is the same.
   1.170 +        /// Sets the iterator to the given node of the given digraph.
   1.171 +        ///
   1.172          NodeIt(const Digraph&, const Node&) { }
   1.173          /// Next node.
   1.174  
   1.175 @@ -157,7 +148,7 @@
   1.176        };
   1.177  
   1.178  
   1.179 -      /// Class for identifying an arc of the digraph
   1.180 +      /// The arc type of the digraph
   1.181  
   1.182        /// This class identifies an arc of the digraph. It also serves
   1.183        /// as a base class of the arc iterators,
   1.184 @@ -166,207 +157,214 @@
   1.185        public:
   1.186          /// Default constructor
   1.187  
   1.188 -        /// @warning The default constructor sets the iterator
   1.189 -        /// to an undefined value.
   1.190 +        /// Default constructor.
   1.191 +        /// \warning It sets the object to an undefined value.
   1.192          Arc() { }
   1.193          /// Copy constructor.
   1.194  
   1.195          /// Copy constructor.
   1.196          ///
   1.197          Arc(const Arc&) { }
   1.198 -        /// Initialize the iterator to be invalid.
   1.199 +        /// %Invalid constructor \& conversion.
   1.200  
   1.201 -        /// Initialize the iterator to be invalid.
   1.202 -        ///
   1.203 +        /// Initializes the object to be invalid.
   1.204 +        /// \sa Invalid for more details.
   1.205          Arc(Invalid) { }
   1.206          /// Equality operator
   1.207  
   1.208 +        /// Equality operator.
   1.209 +        ///
   1.210          /// Two iterators are equal if and only if they point to the
   1.211 -        /// same object or both are invalid.
   1.212 +        /// same object or both are \c INVALID.
   1.213          bool operator==(Arc) const { return true; }
   1.214          /// Inequality operator
   1.215  
   1.216 -        /// \sa operator==(Arc n)
   1.217 -        ///
   1.218 +        /// Inequality operator.
   1.219          bool operator!=(Arc) const { return true; }
   1.220  
   1.221          /// Artificial ordering operator.
   1.222  
   1.223 -        /// To allow the use of digraph descriptors as key type in std::map or
   1.224 -        /// similar associative container we require this.
   1.225 +        /// Artificial ordering operator.
   1.226          ///
   1.227 -        /// \note This operator only have to define some strict ordering of
   1.228 -        /// the items; this order has nothing to do with the iteration
   1.229 -        /// ordering of the items.
   1.230 +        /// \note This operator only has to define some strict ordering of
   1.231 +        /// the arcs; this order has nothing to do with the iteration
   1.232 +        /// ordering of the arcs.
   1.233          bool operator<(Arc) const { return false; }
   1.234        };
   1.235  
   1.236 -      /// This iterator goes trough the outgoing arcs of a node.
   1.237 +      /// Iterator class for the outgoing arcs of a node.
   1.238  
   1.239        /// This iterator goes trough the \e outgoing arcs of a certain node
   1.240        /// of a digraph.
   1.241 -      /// Its usage is quite simple, for example you can count the number
   1.242 +      /// Its usage is quite simple, for example, you can count the number
   1.243        /// of outgoing arcs of a node \c n
   1.244 -      /// in digraph \c g of type \c Digraph as follows.
   1.245 +      /// in a digraph \c g of type \c %Digraph as follows.
   1.246        ///\code
   1.247        /// int count=0;
   1.248 -      /// for (Digraph::OutArcIt e(g, n); e!=INVALID; ++e) ++count;
   1.249 +      /// for (Digraph::OutArcIt a(g, n); a!=INVALID; ++a) ++count;
   1.250        ///\endcode
   1.251 -
   1.252        class OutArcIt : public Arc {
   1.253        public:
   1.254          /// Default constructor
   1.255  
   1.256 -        /// @warning The default constructor sets the iterator
   1.257 -        /// to an undefined value.
   1.258 +        /// Default constructor.
   1.259 +        /// \warning It sets the iterator to an undefined value.
   1.260          OutArcIt() { }
   1.261          /// Copy constructor.
   1.262  
   1.263          /// Copy constructor.
   1.264          ///
   1.265          OutArcIt(const OutArcIt& e) : Arc(e) { }
   1.266 -        /// Initialize the iterator to be invalid.
   1.267 +        /// %Invalid constructor \& conversion.
   1.268  
   1.269 -        /// Initialize the iterator to be invalid.
   1.270 +        /// Initializes the iterator to be invalid.
   1.271 +        /// \sa Invalid for more details.
   1.272 +        OutArcIt(Invalid) { }
   1.273 +        /// Sets the iterator to the first outgoing arc.
   1.274 +
   1.275 +        /// Sets the iterator to the first outgoing arc of the given node.
   1.276          ///
   1.277 -        OutArcIt(Invalid) { }
   1.278 -        /// This constructor sets the iterator to the first outgoing arc.
   1.279 +        OutArcIt(const Digraph&, const Node&) { }
   1.280 +        /// Sets the iterator to the given arc.
   1.281  
   1.282 -        /// This constructor sets the iterator to the first outgoing arc of
   1.283 -        /// the node.
   1.284 -        OutArcIt(const Digraph&, const Node&) { }
   1.285 -        /// Arc -> OutArcIt conversion
   1.286 -
   1.287 -        /// Sets the iterator to the value of the trivial iterator.
   1.288 -        /// This feature necessitates that each time we
   1.289 -        /// iterate the arc-set, the iteration order is the same.
   1.290 +        /// Sets the iterator to the given arc of the given digraph.
   1.291 +        ///
   1.292          OutArcIt(const Digraph&, const Arc&) { }
   1.293 -        ///Next outgoing arc
   1.294 +        /// Next outgoing arc
   1.295  
   1.296          /// Assign the iterator to the next
   1.297          /// outgoing arc of the corresponding node.
   1.298          OutArcIt& operator++() { return *this; }
   1.299        };
   1.300  
   1.301 -      /// This iterator goes trough the incoming arcs of a node.
   1.302 +      /// Iterator class for the incoming arcs of a node.
   1.303  
   1.304        /// This iterator goes trough the \e incoming arcs of a certain node
   1.305        /// of a digraph.
   1.306 -      /// Its usage is quite simple, for example you can count the number
   1.307 -      /// of outgoing arcs of a node \c n
   1.308 -      /// in digraph \c g of type \c Digraph as follows.
   1.309 +      /// Its usage is quite simple, for example, you can count the number
   1.310 +      /// of incoming arcs of a node \c n
   1.311 +      /// in a digraph \c g of type \c %Digraph as follows.
   1.312        ///\code
   1.313        /// int count=0;
   1.314 -      /// for(Digraph::InArcIt e(g, n); e!=INVALID; ++e) ++count;
   1.315 +      /// for(Digraph::InArcIt a(g, n); a!=INVALID; ++a) ++count;
   1.316        ///\endcode
   1.317 -
   1.318        class InArcIt : public Arc {
   1.319        public:
   1.320          /// Default constructor
   1.321  
   1.322 -        /// @warning The default constructor sets the iterator
   1.323 -        /// to an undefined value.
   1.324 +        /// Default constructor.
   1.325 +        /// \warning It sets the iterator to an undefined value.
   1.326          InArcIt() { }
   1.327          /// Copy constructor.
   1.328  
   1.329          /// Copy constructor.
   1.330          ///
   1.331          InArcIt(const InArcIt& e) : Arc(e) { }
   1.332 -        /// Initialize the iterator to be invalid.
   1.333 +        /// %Invalid constructor \& conversion.
   1.334  
   1.335 -        /// Initialize the iterator to be invalid.
   1.336 +        /// Initializes the iterator to be invalid.
   1.337 +        /// \sa Invalid for more details.
   1.338 +        InArcIt(Invalid) { }
   1.339 +        /// Sets the iterator to the first incoming arc.
   1.340 +
   1.341 +        /// Sets the iterator to the first incoming arc of the given node.
   1.342          ///
   1.343 -        InArcIt(Invalid) { }
   1.344 -        /// This constructor sets the iterator to first incoming arc.
   1.345 +        InArcIt(const Digraph&, const Node&) { }
   1.346 +        /// Sets the iterator to the given arc.
   1.347  
   1.348 -        /// This constructor set the iterator to the first incoming arc of
   1.349 -        /// the node.
   1.350 -        InArcIt(const Digraph&, const Node&) { }
   1.351 -        /// Arc -> InArcIt conversion
   1.352 -
   1.353 -        /// Sets the iterator to the value of the trivial iterator \c e.
   1.354 -        /// This feature necessitates that each time we
   1.355 -        /// iterate the arc-set, the iteration order is the same.
   1.356 +        /// Sets the iterator to the given arc of the given digraph.
   1.357 +        ///
   1.358          InArcIt(const Digraph&, const Arc&) { }
   1.359          /// Next incoming arc
   1.360  
   1.361 -        /// Assign the iterator to the next inarc of the corresponding node.
   1.362 -        ///
   1.363 +        /// Assign the iterator to the next
   1.364 +        /// incoming arc of the corresponding node.
   1.365          InArcIt& operator++() { return *this; }
   1.366        };
   1.367 -      /// This iterator goes through each arc.
   1.368  
   1.369 -      /// This iterator goes through each arc of a digraph.
   1.370 -      /// Its usage is quite simple, for example you can count the number
   1.371 -      /// of arcs in a digraph \c g of type \c Digraph as follows:
   1.372 +      /// Iterator class for the arcs.
   1.373 +
   1.374 +      /// This iterator goes through each arc of the digraph.
   1.375 +      /// Its usage is quite simple, for example, you can count the number
   1.376 +      /// of arcs in a digraph \c g of type \c %Digraph as follows:
   1.377        ///\code
   1.378        /// int count=0;
   1.379 -      /// for(Digraph::ArcIt e(g); e!=INVALID; ++e) ++count;
   1.380 +      /// for(Digraph::ArcIt a(g); a!=INVALID; ++a) ++count;
   1.381        ///\endcode
   1.382        class ArcIt : public Arc {
   1.383        public:
   1.384          /// Default constructor
   1.385  
   1.386 -        /// @warning The default constructor sets the iterator
   1.387 -        /// to an undefined value.
   1.388 +        /// Default constructor.
   1.389 +        /// \warning It sets the iterator to an undefined value.
   1.390          ArcIt() { }
   1.391          /// Copy constructor.
   1.392  
   1.393          /// Copy constructor.
   1.394          ///
   1.395          ArcIt(const ArcIt& e) : Arc(e) { }
   1.396 -        /// Initialize the iterator to be invalid.
   1.397 +        /// %Invalid constructor \& conversion.
   1.398  
   1.399 -        /// Initialize the iterator to be invalid.
   1.400 +        /// Initializes the iterator to be invalid.
   1.401 +        /// \sa Invalid for more details.
   1.402 +        ArcIt(Invalid) { }
   1.403 +        /// Sets the iterator to the first arc.
   1.404 +
   1.405 +        /// Sets the iterator to the first arc of the given digraph.
   1.406          ///
   1.407 -        ArcIt(Invalid) { }
   1.408 -        /// This constructor sets the iterator to the first arc.
   1.409 +        explicit ArcIt(const Digraph& g) { ignore_unused_variable_warning(g); }
   1.410 +        /// Sets the iterator to the given arc.
   1.411  
   1.412 -        /// This constructor sets the iterator to the first arc of \c g.
   1.413 -        ///@param g the digraph
   1.414 -        ArcIt(const Digraph& g) { ignore_unused_variable_warning(g); }
   1.415 -        /// Arc -> ArcIt conversion
   1.416 -
   1.417 -        /// Sets the iterator to the value of the trivial iterator \c e.
   1.418 -        /// This feature necessitates that each time we
   1.419 -        /// iterate the arc-set, the iteration order is the same.
   1.420 +        /// Sets the iterator to the given arc of the given digraph.
   1.421 +        ///
   1.422          ArcIt(const Digraph&, const Arc&) { }
   1.423 -        ///Next arc
   1.424 +        /// Next arc
   1.425  
   1.426          /// Assign the iterator to the next arc.
   1.427 +        ///
   1.428          ArcIt& operator++() { return *this; }
   1.429        };
   1.430 -      ///Gives back the target node of an arc.
   1.431  
   1.432 -      ///Gives back the target node of an arc.
   1.433 +      /// \brief The source node of the arc.
   1.434        ///
   1.435 -      Node target(Arc) const { return INVALID; }
   1.436 -      ///Gives back the source node of an arc.
   1.437 -
   1.438 -      ///Gives back the source node of an arc.
   1.439 -      ///
   1.440 +      /// Returns the source node of the given arc.
   1.441        Node source(Arc) const { return INVALID; }
   1.442  
   1.443 -      /// \brief Returns the ID of the node.
   1.444 +      /// \brief The target node of the arc.
   1.445 +      ///
   1.446 +      /// Returns the target node of the given arc.
   1.447 +      Node target(Arc) const { return INVALID; }
   1.448 +
   1.449 +      /// \brief The ID of the node.
   1.450 +      ///
   1.451 +      /// Returns the ID of the given node.
   1.452        int id(Node) const { return -1; }
   1.453  
   1.454 -      /// \brief Returns the ID of the arc.
   1.455 +      /// \brief The ID of the arc.
   1.456 +      ///
   1.457 +      /// Returns the ID of the given arc.
   1.458        int id(Arc) const { return -1; }
   1.459  
   1.460 -      /// \brief Returns the node with the given ID.
   1.461 +      /// \brief The node with the given ID.
   1.462        ///
   1.463 -      /// \pre The argument should be a valid node ID in the graph.
   1.464 +      /// Returns the node with the given ID.
   1.465 +      /// \pre The argument should be a valid node ID in the digraph.
   1.466        Node nodeFromId(int) const { return INVALID; }
   1.467  
   1.468 -      /// \brief Returns the arc with the given ID.
   1.469 +      /// \brief The arc with the given ID.
   1.470        ///
   1.471 -      /// \pre The argument should be a valid arc ID in the graph.
   1.472 +      /// Returns the arc with the given ID.
   1.473 +      /// \pre The argument should be a valid arc ID in the digraph.
   1.474        Arc arcFromId(int) const { return INVALID; }
   1.475  
   1.476 -      /// \brief Returns an upper bound on the node IDs.
   1.477 +      /// \brief An upper bound on the node IDs.
   1.478 +      ///
   1.479 +      /// Returns an upper bound on the node IDs.
   1.480        int maxNodeId() const { return -1; }
   1.481  
   1.482 -      /// \brief Returns an upper bound on the arc IDs.
   1.483 +      /// \brief An upper bound on the arc IDs.
   1.484 +      ///
   1.485 +      /// Returns an upper bound on the arc IDs.
   1.486        int maxArcId() const { return -1; }
   1.487  
   1.488        void first(Node&) const {}
   1.489 @@ -392,50 +390,51 @@
   1.490        // Dummy parameter.
   1.491        int maxId(Arc) const { return -1; }
   1.492  
   1.493 +      /// \brief The opposite node on the arc.
   1.494 +      ///
   1.495 +      /// Returns the opposite node on the given arc.
   1.496 +      Node oppositeNode(Node, Arc) const { return INVALID; }
   1.497 +
   1.498        /// \brief The base node of the iterator.
   1.499        ///
   1.500 -      /// Gives back the base node of the iterator.
   1.501 -      /// It is always the target of the pointed arc.
   1.502 -      Node baseNode(const InArcIt&) const { return INVALID; }
   1.503 +      /// Returns the base node of the given outgoing arc iterator
   1.504 +      /// (i.e. the source node of the corresponding arc).
   1.505 +      Node baseNode(OutArcIt) const { return INVALID; }
   1.506  
   1.507        /// \brief The running node of the iterator.
   1.508        ///
   1.509 -      /// Gives back the running node of the iterator.
   1.510 -      /// It is always the source of the pointed arc.
   1.511 -      Node runningNode(const InArcIt&) const { return INVALID; }
   1.512 +      /// Returns the running node of the given outgoing arc iterator
   1.513 +      /// (i.e. the target node of the corresponding arc).
   1.514 +      Node runningNode(OutArcIt) const { return INVALID; }
   1.515  
   1.516        /// \brief The base node of the iterator.
   1.517        ///
   1.518 -      /// Gives back the base node of the iterator.
   1.519 -      /// It is always the source of the pointed arc.
   1.520 -      Node baseNode(const OutArcIt&) const { return INVALID; }
   1.521 +      /// Returns the base node of the given incomming arc iterator
   1.522 +      /// (i.e. the target node of the corresponding arc).
   1.523 +      Node baseNode(InArcIt) const { return INVALID; }
   1.524  
   1.525        /// \brief The running node of the iterator.
   1.526        ///
   1.527 -      /// Gives back the running node of the iterator.
   1.528 -      /// It is always the target of the pointed arc.
   1.529 -      Node runningNode(const OutArcIt&) const { return INVALID; }
   1.530 +      /// Returns the running node of the given incomming arc iterator
   1.531 +      /// (i.e. the source node of the corresponding arc).
   1.532 +      Node runningNode(InArcIt) const { return INVALID; }
   1.533  
   1.534 -      /// \brief The opposite node on the given arc.
   1.535 +      /// \brief Standard graph map type for the nodes.
   1.536        ///
   1.537 -      /// Gives back the opposite node on the given arc.
   1.538 -      Node oppositeNode(const Node&, const Arc&) const { return INVALID; }
   1.539 -
   1.540 -      /// \brief Reference map of the nodes to type \c T.
   1.541 -      ///
   1.542 -      /// Reference map of the nodes to type \c T.
   1.543 +      /// Standard graph map type for the nodes.
   1.544 +      /// It conforms to the ReferenceMap concept.
   1.545        template<class T>
   1.546        class NodeMap : public ReferenceMap<Node, T, T&, const T&> {
   1.547        public:
   1.548  
   1.549 -        ///\e
   1.550 -        NodeMap(const Digraph&) { }
   1.551 -        ///\e
   1.552 +        /// Constructor
   1.553 +        explicit NodeMap(const Digraph&) { }
   1.554 +        /// Constructor with given initial value
   1.555          NodeMap(const Digraph&, T) { }
   1.556  
   1.557        private:
   1.558          ///Copy constructor
   1.559 -        NodeMap(const NodeMap& nm) : 
   1.560 +        NodeMap(const NodeMap& nm) :
   1.561            ReferenceMap<Node, T, T&, const T&>(nm) { }
   1.562          ///Assignment operator
   1.563          template <typename CMap>
   1.564 @@ -445,17 +444,19 @@
   1.565          }
   1.566        };
   1.567  
   1.568 -      /// \brief Reference map of the arcs to type \c T.
   1.569 +      /// \brief Standard graph map type for the arcs.
   1.570        ///
   1.571 -      /// Reference map of the arcs to type \c T.
   1.572 +      /// Standard graph map type for the arcs.
   1.573 +      /// It conforms to the ReferenceMap concept.
   1.574        template<class T>
   1.575        class ArcMap : public ReferenceMap<Arc, T, T&, const T&> {
   1.576        public:
   1.577  
   1.578 -        ///\e
   1.579 -        ArcMap(const Digraph&) { }
   1.580 -        ///\e
   1.581 +        /// Constructor
   1.582 +        explicit ArcMap(const Digraph&) { }
   1.583 +        /// Constructor with given initial value
   1.584          ArcMap(const Digraph&, T) { }
   1.585 +
   1.586        private:
   1.587          ///Copy constructor
   1.588          ArcMap(const ArcMap& em) :