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updated boost from 1_33_1 to 1_34_1
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2<!--
3  -- Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine 2000
4  --
5  -- Distributed under the Boost Software License, Version 1.0.
6  -- (See accompanying file LICENSE_1_0.txt or copy at
7  -- http://www.boost.org/LICENSE_1_0.txt)
8  -->
9<Head>
10<Title>Boost Graph Library: EventVisitor</Title>
11<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" 
12        ALINK="#ff0000"> 
13<IMG SRC="../../../boost.png" 
14     ALT="C++ Boost" width="277" height="86"> 
15
16<BR Clear>
17
18<H1>EventVisitor Concept</H1>
19
20This concept defines the interface for single-event visitors. An
21EventVisitor has an apply member function (<tt>operator()</tt>) which
22is invoked within the graph algorithm at the event-point specified by
23the <tt>event_filter</tt> typedef within the
24EventVisitor. EventVisitor's can be combined into an <a
25href="./EventVisitorList.html">EventVistorList</a>.
26
27<p>
28The following is the list of event tags that can be invoked in BGL
29algorithms. Each tag corresponds to a member function of the visitor
30for an algorithm. For example, the <a
31href="./BFSVisitor.html">BFSVisitor</a> of <a
32href="./breadth_first_search.html"><tt>breadth_first_search()</tt></a>
33has a <tt>cycle_edge()</tt> member function. The corresponding tag is
34<tt>on_cycle_edge</tt>. The first argument is the event visitor's
35<tt>operator()</tt> must be either an edge or vertex descriptor
36depending on the event tag.
37
38<pre>
39namespace boost {
40  struct on_initialize_vertex { };
41  struct on_start_vertex { };
42  struct on_discover_vertex { };
43  struct on_examine_edge { };
44  struct on_tree_edge { };
45  struct on_cycle_edge { };
46  struct on_finish_vertex { };
47  struct on_forward_or_cross_edge { };
48  struct on_back_edge { };
49  struct on_edge_relaxed { };
50  struct on_edge_not_relaxed { };
51  struct on_edge_minimized { };
52  struct on_edge_not_minimized { };
53} // namespace boost
54</pre>
55
56
57<h3>Refinement of</h3>
58
59<a href="../../utility/CopyConstructible.html">Copy Constructible</a>
60(copying a visitor should be a lightweight operation).
61
62<h3>Notation</h3>
63
64<Table>
65<TR>
66<TD><tt>G</tt></TD>
67<TD>A type that is a model of <a href="./Graph.html">Graph</a>.</TD>
68</TR>
69
70<TR>
71<TD><tt>g</tt></TD>
72<TD>An object of type <tt>G</tt>.</TD>
73</TR>
74
75<TR>
76<TD><tt>V</tt></TD>
77<TD>A type that is a model of EventVisitor.</TD>
78</TR>
79
80<TR>
81<TD><tt>vis</tt></TD>
82<TD>An object of type <tt>V</tt>.</TD>
83</TR>
84
85<TR>
86<TD><tt>x</tt></TD>
87<TD>An object of type
88<tt>boost::graph_traits&lt;G&gt;::vertex_descriptor</tt>
89or <tt>boost::graph_traits&lt;G&gt;::edge_descriptor</tt>.</TD>
90</TR>
91
92</table>
93
94<h3>Associated Types</h3>
95
96<Table border>
97
98<TR>
99<TD>Event Filter </TD>
100<TD><TT>V::event_filter</TT></TD>
101<TD>
102A tag struct to specify on which event the visitor should be invoked.
103</TD>
104</TR>
105
106</table>
107
108<h3>Valid Expressions</h3>
109
110<Table border>
111
112<tr>
113<th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th>
114</tr>
115
116<tr>
117<td>Apply Visitor</td>
118<td><TT>vis(x, g)</TT></TD>
119<TD><TT>void</TT></TD>
120<TD>
121Invokes the visitor operation on object <tt>x</tt>, which is
122either a vertex or edge descriptor of the graph.
123</TD>
124</TR>
125
126
127</table>
128
129
130<h3>Models</h3>
131
132<ul>
133 <li><a
134 href="./predecessor_recorder.html"><tt>predecessor_recorder</tt></a>
135 <li><a href="./distance_recorder.html"><tt>distance_recorder</tt></a>
136 <li><a href="./time_stamper.html"><tt>time_stamper</tt></a>
137 <li><a href="./property_writer.html"><tt>property_writer</tt></a>
138 <li><a href="./null_visitor.html"><tt>null_visitor</tt></a>
139</ul>
140
141<h3>See Also</h3>
142
143<a href="./EventVisitorList.html">EventVisitorList</a>,
144<a href="./visitor_concepts.html">Visitor concepts</a>
145
146<br>
147<HR>
148<TABLE>
149<TR valign=top>
150<TD nowrap>Copyright &copy 2000-2001</TD><TD>
151<A HREF="../../../people/jeremy_siek.htm">Jeremy Siek</A>,
152Indiana University (<A
153HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br>
154<A HREF="../../../people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
155<A HREF=http://www.osl.iu.edu/~lums>Andrew Lumsdaine</A>,
156Indiana University (<A
157HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
158</TD></TR></TABLE>
159
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