131 lines
3.4 KiB
HTML
131 lines
3.4 KiB
HTML
<html>
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<head>
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<!-- Copyright 2007 Aaron Windsor
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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-->
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<title>AddEdgeVisitor Concept</title>
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</head>
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<body alink="#ff0000"
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bgcolor="#ffffff"
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link="#0000ee"
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text="#000000"
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vlink="#551a8b">
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<img src="../../../boost.png" alt="C++ Boost" height="86" width="277">
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<br clear="">
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<h1>AddEdgeVisitor Concept</h1>
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The AddEdgeVisitor concept exists to allow for some indirection in algorithms
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that modify graphs by adding edges. In such algorithms, it may be convenient
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to perform additional operations (such as updating an edge index map) at
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points in the algorithm where an edge addition occurs. Replacing calls to
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to <tt>add_edge</tt> with calls to <tt>AddEdgeVisitor::visit_vertex_pair</tt>
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allows for such operations to be defined independently from the algorithm.
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<h3>Notation</h3>
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<table>
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<tbody>
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<tr>
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<td> <tt>Visitor</tt> </td>
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<td> is a type that models the AddEdgeVisitor concept </td>
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</tr>
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<tr>
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<td> <tt>vis</tt> </td>
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<td> is an object of type Visitor </td>
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</tr>
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<tr>
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<td> <tt>Graph</tt> </td>
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<td> is the type of a graph </td>
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</tr>
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<tr>
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<td> <tt>u,v</tt> </td>
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<td> are objects of type <tt>graph_traits<Graph>::vertex_descriptor</tt>
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</td>
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</tr>
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<tr>
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<td> <tt>e</tt> </td>
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<td> is an object of type <tt>graph_traits<Graph>::edge_descriptor</tt>
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</td>
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</tr>
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<tr>
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<td> <tt>v</tt> </td>
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<td> is an object of type <tt>graph_traits<Graph>::vertex_descriptor</tt>
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</td>
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</tr><tr>
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<td>
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</td></tr></tbody></table>
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<h3>Associated Types</h3>
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None
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<h3>Valid Expressions</h3>
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<p>
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<table border="1">
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<tbody><tr><th>Name</th><th>Expression</th><th>Return Type</th>
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<th>Description</th>
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</tr><tr>
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<td> Add an Edge </td>
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<td> <tt>vis.visit_vertex_pair(u, v, g)</tt> </td>
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<td> <tt>void</tt></td>
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<td> Invoked every time an edge between vertices <tt>u</tt> and <tt>v</tt>
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should be added to the graph <tt>g</tt>.
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</td></tr>
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</tbody></table>
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</p><h3>Models</h3>
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Two models of this concept are defined in the file
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<a href="../../../boost/graph/planar_detail/add_edge_visitors.hpp">
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<tt>add_edge_visitors.hpp</tt></a>:
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<ul>
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<li><tt>default_add_edge_visitor</tt>: The constructor of this class takes
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no arguments.<tt>visit_vertex_pair(u, v, g)</tt> is just a dispatch to
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<tt>add_edge(u, v, g)</tt>.
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<li><tt>edge_index_update_visitor</tt>: The constructor of this class takes
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two arguments: the first, an EdgeIndexMap,
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is a <a href="../../property_map/doc/ReadWritePropertyMap.html">
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ReadWritePropertyMap</a> that maps each edge in the associated graph
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<tt>g</tt> to a distinct integer in the range <tt>[0, num_edges(g))</tt>.
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The second argument is the number of edges in the underlying graph, which
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serves as the "next available index" counter within the visitor.
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For example, in the case the graph used has an initialized interior
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edge index, the <tt>edge_index_update_visitor</tt> constructor should be
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called with <tt>get(edge_index, g)</tt> as the edge index and
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<tt>num_edges(g)</tt> as the next available index. When
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<tt>visit_vertex_pair(u, v, g)</tt> is called, the
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<tt>edge_index_update_visitor</tt> will add the edge <i>(u,v)</i> to the graph
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and update the edge index for the newly created edge.
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</ul>
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<p>
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<br>
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</p><hr>
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Copyright <20> 2007 Aaron Windsor (<a href="mailto:aaron.windsor@gmail.com">
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aaron.windsor@gmail.com</a>)
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</body></html>
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