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<Head>
<Title>Boost Graph Library: distance_recorder</Title>
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<H1>
<pre>
distance_recorder&lt;DistanceMap, EventTag&gt;
</pre>
</H1>

This is an <a href="./EventVisitor.html">EventVisitor</a> that records
the distance of a vertex (using a <a
href="property_map.html">property map</a>) from some
source vertex during a graph search. When applied to edge <i>e =
(u,v)</i>, the distance of <i>v</i> is recorded to be one more than
the distance of <i>u</i>. The distance recorder is typically used with
the <tt>on_tree_edge</tt> or <tt>on_relax_edge</tt> events and
cannot be used with vertex events.

<p>
<tt>distance_recorder</tt> can be used with graph algorithms by
wrapping it with the algorithm specific adaptor, such as <a
href="./bfs_visitor.html"><tt>bfs_visitor</tt></a> and <a
href="./dfs_visitor.html"><tt>dfs_visitor</tt></a>. Also, this event
visitor can be combined with other event visitors using
<tt>std::pair</tt> to form an EventVisitorList.

<h3>Example</h3>

See the example for <a href="./bfs_visitor.html"><tt>bfs_visitor</tt></a>.

<h3>Model of</h3>

<a href="./EventVisitor.html">EventVisitor</a>


<H3>Where Defined</H3>

<P>
<a href="../../../boost/graph/visitors.hpp">
<TT>boost/graph/visitors.hpp</TT></a>

<H3>Template Parameters</H3>

<P>
<TABLE border>
<TR>
<th>Parameter</th><th>Description</th><th>Default</th>
</tr>

<TR><TD><TT>DistanceMap</TT></TD>
<TD>
A <a
href="../../property_map/doc/WritablePropertyMap.html">WritablePropertyMap</a>
where the key type and the value type are the vertex descriptor type
of the graph.
</TD>
<TD>&nbsp;</TD>
</TR>

<TR><TD><TT>EventTag</TT></TD>
<TD>
The tag to specify when the <tt>distance_recorder</tt> should be
applied during the graph algorithm. <tt>EventTag</tt> must be an
edge event.
</TD>
<TD>&nbsp;</TD>
</TR>

</table>

<H2>Associated Types</H2>

<table border>

<tr>
<th>Type</th><th>Description</th>
</tr>

<tr>
<td><tt>distance_recorder::event_filter</tt></td>
<td>
This will be the same type as the template parameter <tt>EventTag</tt>.
</td>
</tr>

</table>

<h3>Member Functions</h3>

<p>

<table border>
<tr>
<th>Member</th><th>Description</th>
</tr>

<tr>
<td><tt>
distance_recorder(DistanceMap pa);
</tt></td>
<td>
Construct a distance recorder object with distance property map
<tt>pa</tt>.
</td>
</tr>

<tr>
<td><tt>
template &lt;class Edge, class Graph&gt;<br>
void operator()(Edge e, const Graph& g);
</tt></td>
<td>
Given edge <i>e = (u,v)</i>, this records the distance of <i>v</i> as 
one plus the distance of <i>u</i>.
</td>
</tr>

</table>

<h3>Non-Member Functions</h3>

<table border>
<tr>
<th>Function</th><th>Description</th>
</tr>

<tr><td><tt>
template &lt;class DistanceMap, class Tag&gt;<br>
distance_recorder&lt;DistanceMap, Tag&gt; <br>
record_distances(DistanceMap pa, Tag);
</tt></td><td>
A convenient way to create a <tt>distance_recorder</tt>.
</td></tr>

</table>

<h3>See Also</h3>

<a href="./visitor_concepts.html">Visitor concepts</a>
<p>
The following are other event visitors: <a
 href="./predecessor_recorder.html"><tt>predecessor_recorder</tt></a>,
<a href="./time_stamper.html"><tt>time_stamper</tt></a>,
and <a href="./property_writer.html"><tt>property_writer</tt></a>.


<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 2000-2001</TD><TD>
<A HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</A>,
Indiana University (<A
HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br>
<A HREF="http://www.boost.org/people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
<A HREF="https://homes.cs.washington.edu/~al75">Andrew Lumsdaine</A>,
Indiana University (<A
HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
</TD></TR></TABLE>

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