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AddEdgeVisitor Concept

The AddEdgeVisitor concept exists to allow for some indirection in algorithms that modify graphs by adding edges. In such algorithms, it may be convenient to perform additional operations (such as updating an edge index map) at points in the algorithm where an edge addition occurs. Replacing calls to to add_edge with calls to AddEdgeVisitor::visit_vertex_pair allows for such operations to be defined independently from the algorithm.

Notation

Visitor is a type that models the AddEdgeVisitor concept

vis

is an object of type Visitor

Graph

is the type of a graph

u,v

are objects of type graph_traits<Graph>::vertex_descriptor

e

is an object of type graph_traits<Graph>::edge_descriptor

v

is an object of type graph_traits<Graph>::vertex_descriptor

Associated Types

None

Valid Expressions

Name Expression Return Type Description

Add an Edge

vis.visit_vertex_pair(u, v, g)

void

Invoked every time an edge between vertices u and v should be added to the graph g.

Models

Two models of this concept are defined in the file add_edge_visitors.hpp:

  • default_add_edge_visitor: The constructor of this class takes no arguments.visit_vertex_pair(u, v, g) is just a dispatch to add_edge(u, v, g).

  • edge_index_update_visitor: The constructor of this class takes two arguments: the first, an EdgeIndexMap, is a ReadWritePropertyMap that maps each edge in the associated graph g to a distinct integer in the range [0, num_edges(g)). The second argument is the number of edges in the underlying graph, which serves as the "next available index" counter within the visitor. For example, in the case the graph used has an initialized interior edge index, the edge_index_update_visitor constructor should be called with get(edge_index, g) as the edge index and num_edges(g) as the next available index. When visit_vertex_pair(u, v, g) is called, the edge_index_update_visitor will add the edge (u,v) to the graph and update the edge index for the newly created edge.

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