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--Foundation visitor is just the name we use for visitor classes that are -used inside the implementation of BGL algorithms. Typically you will -never need to see or use these classes, however perhaps they will be -of interest as examples or can reused in some unforeseen -circumstances. - -
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-There are a handful of visitors defined by BGL, but the visitor -mechanism is mainly intended as a way for users to extend BGL with -their own custom visitors. Use the BGL visitors as examples for how to -implement you own. The visitors in this section are models of UserVisitor. - -
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-This is a visitor that does nothing. It is useful as a base class for -user-defined visitors that only implement some of the visitor -methods. The unimplemented methods will default to the empty ones in -the base_visitor class. Due to deficiencies in VC++ this class -can not be used with that compiler. Use base_visitor instead -if you need VC++ portability. - -
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-null_visitor::category --The category for this visitor is every_edge_tag. - -
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-template <class Vertex>
-void null_visitor::initialize(Vertex u) { }
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-- -
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-template <class Vertex>
-void null_visitor::start(Vertex s) { }
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-- -
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-template <class Vertex>
-void null_visitor::discover(Vertex s) { }
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-- -
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-template <class Vertex>
-void null_visitor::finish(Vertex s) { }
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-- -
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-template <class Edge, class Graph>
-void null_visitor::process(Edge e, Graph& g) { }
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-- -
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-base_visitor<Visitor> -- -
-This is a visitor that does nothing. It is useful as a base class for -user-defined visitors that only implement some of the visitor -methods. The unimplemented methods will default to the empty ones in -the base_visitor class. The template argument Visitor -must be the deriving visitor class. This class is a workaround for -VC++. If VC++ portability is not an issue use null_visitor -instead. - -
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-base_visitor::category --The category for this visitor is every_edge_tag. - -
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-template <class Vertex>
-void base_visitor::initialize(Vertex u) { }
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-- -
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-template <class Vertex>
-void base_visitor::start(Vertex s) { }
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-- -
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-template <class Vertex>
-void base_visitor::discover(Vertex s) { }
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-- -
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-template <class Vertex>
-void base_visitor::finish(Vertex s) { }
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-- -
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-template <class Edge, class Graph>
-void base_visitor::process(Edge e, Graph& g) { }
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-- -
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-distance_visitor<Distance> -- -
-The distance visitor records the distance from the starting vertex to -each vertex in a search tree. The type of search tree depends on the -algorithm being applied. - -
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| Distance | -Must be a model of ReadWritePropertyAccessor. | -
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-Visitor - -
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-distance_visitor::category --The visitor category for this class is tree_edge_tag. - -
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-distance_visitor::distance_visitor(Distance p) --Constructor. - -
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-template <class Vertex> -distance_visitor::initialize(Vertex u) --This initializes the distance property for all the vertices -to std::numeric_limits<T>::max() where T is -the value type of the distance property accessor. - -
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-template <class Vertex> -distance_visitor::start(Vertex u) --This initializes the distance of the starting vertex to zero. - -
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-template <class Edge, class Graph> -distance_visitor::process(Edge e, Graph& g) --This records the distance of for the target(e,g) as -d[source(e,g)] + 1. - -
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-predecessor_visitor<Predecessor> -- -
-The predecessor visitor records the predecessors (or parents) of the -nodes in a search tree, where the search tree depends on the kind of -graph search algorithm being applied. - -
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| Predecessor | -Must be a model of WritablePropertyAccessor. | -
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-Visitor - -
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-predecessor_visitor::category --The visitor category for this class is tree_edge_tag. - -
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-predecessor_visitor::predecessor_visitor(Predecessor p) --Constructor. - -
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-template <class Edge, class Graph> -predecessor_visitor::process(Edge e, Graph& g) --This method records the predecessor (or parent), where -target(e) is the parent and source(e) is the child. -The implementation is simply p[target(e,g)] = source(e,g). -
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-timestamp_visitor<DiscoverTime,FinishTime> -- -
-The time-stamp visitor is for recording the ``discover'' and -``finish'' order for vertices during a graph search. The time-stamp -starts at zero and increments one each time a vertex is discovered or -finished. - -
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| DiscoverTime | -Must be a model of WritablePropertyAccessor. | -
| FinishTime | -Must be a model of WritablePropertyAccessor. | -
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-timestamp_visitor::category --The visitor category for this class is tree_edge_tag. - -
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-timestamp_visitor::timestamp_visitor(DiscoverTime d, FinishTime f) --Constructor. - -
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-template <class Vertex> -timestamp_visitor::discover(Vertex u) --This method records the discover time for vertex u. The -implementation is simply d[u] = ++time. - -
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-template <class Vertex> -timestamp_visitor::finish(Vertex u) --This method records the finish time for vertex u. The -implementation is simply f[u] = ++time. - -
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| Copyright © 2000 |
-Jeremy Siek,
-Univ.of Notre Dame (jsiek@lsc.nd.edu) -Lie-Quan Lee, Univ.of Notre Dame (llee1@lsc.nd.edu) -Andrew Lumsdaine, -Univ.of Notre Dame (lums@lsc.nd.edu) - |