1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
<HTML>
<!--
-- Copyright (c) Jeremy Siek 2000
--
-- Distributed under the Boost Software License, Version 1.0.
-- (See accompanying file LICENSE_1_0.txt or copy at
-- http://www.boost.org/LICENSE_1_0.txt)
-->
<Head>
<Title>AdjacencyGraph</Title>
<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
ALINK="#ff0000">
<IMG SRC="../../../boost.png"
ALT="C++ Boost" width="277" height="86">
<BR Clear>
<H2><A NAME="concept:AdjacencyGraph"></A>
AdjacencyGraph
</H2>
The AdjacencyGraph concept provides and interface for efficient access
of the adjacent vertices to a vertex in a graph. This is quite similar
to the <a href="./IncidenceGraph.html">IncidenceGraph</a> concept (the
target of an out-edge is an adjacent vertex). Both concepts are
provided because in some contexts there is only concern for the
vertices, whereas in other contexts the edges are also important.
<H3>Refinement of</H3>
<a href="Graph.html">Graph</a>
<h3>Notation</h3>
<Table>
<TR>
<TD><tt>G</tt></TD>
<TD>A type that is a model of Graph.</TD>
</TR>
<TR>
<TD><tt>g</tt></TD>
<TD>An object of type <tt>G</tt>.</TD>
</TR>
<TR>
<TD><tt>v</tt></TD>
<TD>An object of type <tt>boost::graph_traits<G>::vertex_descriptor</tt>.</TD>
</TR>
</table>
<H3>Associated Types</H3>
<Table border>
<tr>
<td><tt>boost::graph_traits<G>::traversal_category</tt><br><br>
This tag type must be convertible to <tt>adjacency_graph_tag</tt>.
</td>
</tr>
<TR>
<TD><pre>boost::graph_traits<G>::adjacency_iterator</pre>
An adjacency iterator for a vertex <i>v</i> provides access to the
vertices adjacent to <i>v</i>. As such, the value type of an
adjacency iterator is the vertex descriptor type of its graph. An
adjacency iterator must meet the requirements of <a
href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>.
</TD>
</TR>
</table>
<h3>Valid Expressions</h3>
<table border>
<tr>
<td><a name="sec:adjacent-vertices"><TT>adjacent_vertices(v, g)</TT></a></TD>
<TD>
Returns an iterator-range providing access to the vertices adjacent to
vertex <TT>v</TT> in graph <TT>g</TT>.<a
href="#1">[1]</a>
<br> Return type:
<TT>std::pair<adjacency_iterator, adjacency_iterator></TT>
</TD>
</TR>
</table>
<H3>Complexity guarantees</H3>
The <TT>adjacent_vertices()</TT> function must return in constant time.
<H3>See Also</H3>
<a href="./graph_concepts.html">Graph concepts</a>,
<a href="./adjacency_iterator.html"><tt>adjacency_iterator</tt></a>
<H3>Concept Checking Class</H3>
<PRE>
template <class G>
struct AdjacencyGraphConcept
{
typedef typename boost::graph_traits<G>::adjacency_iterator
adjacency_iterator;
void constraints() {
function_requires< IncidenceGraphConcept<G> >();
function_requires< MultiPassInputIteratorConcept<adjacency_iterator> >();
p = adjacent_vertices(v, g);
v = *p.first;
const_constraints(g);
}
void const_constraints(const G& g) {
p = adjacent_vertices(v, g);
}
std::pair<adjacency_iterator,adjacency_iterator> p;
typename boost::graph_traits<G>::vertex_descriptor v;
G g;
};
</PRE>
<h3>Design Rationale</h3>
The AdjacencyGraph concept is somewhat frivolous since <a
href="./IncidenceGraph.html">IncidenceGraph</a> really covers the same
functionality (and more). The AdjacencyGraph concept exists because
there are situations when <tt>adjacent_vertices()</tt> is more
convenient to use than <tt>out_edges()</tt>. If you are constructing a
graph class and do not want to put in the extra work of creating an
adjacency iterator, have no fear. There is an adaptor class named <a
href="./adjacency_iterator.html"> <tt>adjacency_iterator</tt></a> that
you can use to create an adjacency iterator out of an out-edge
iterator.
<h3>Notes</h3>
<a name="1">[1]</a> The case of a
<I>multigraph</I> (where multiple edges can connect the same two
vertices) brings up an issue as to whether the iterators returned by
the <TT>adjacent_vertices()</TT> function access a range that
includes each adjacent vertex once, or whether it should match the
behavior of the <TT>out_edges()</TT> function, and access a
range that may include an adjacent vertex more than once. For now the
behavior is defined to match that of <TT>out_edges()</TT>,
though this decision may need to be reviewed in light of more
experience with graph algorithm implementations.
<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright © 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>)
</TD></TR></TABLE>
</BODY>
</HTML>
|
