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<Title>IteratorConstructibleGraph</Title>
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<H1><A NAME="concept:IteratorConstructibleGraph"></A>
IteratorConstructibleGraph
</H1>

The IteratorConstructibleGraph concept describes the interface for
graph types that can be constructed using a kind of edge iterator. The
edge iterator can be any <a
href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</a>
that dereferences to a pair of integers <i>(i,j)</i>, which represent
an edge that should be in the graph. The two integers <i>i</i> and
<i>j</i> represent vertices where <i>0 <= i < |V|</i> and <i>0 <= j <
|V|</i>.  The edge iterator's value type should be
<tt>std::pair&lt;T,T&gt;</tt> (or at least be a structure that has
members <tt>first</tt> and <tt>second</tt>) and the value type
<tt>T</tt> of the pair must be convertible to the
<tt>vertices_size_type</tt> of the graph (an integer).

There are two valid expressions required by this concept, both of
which are constructors. The first creates a graph object from a
first/last iterator range. The second constructor also takes a
first/last iterator range and in addition requires the number of
vertices and number of edges. For some graph and edge iterator types
the second constructor can be more efficient than the first.

<h3>Example</h3>

The following exampe creates two graph objects from an array of edges
(vertex pairs). The type <tt>Edge*</tt> satisfies the requirements for
an <a
href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</a>
and can therefore be used to construct a graph.

<pre>
  typedef ... IteratorConstructibleGraph;
  typedef boost::graph_traits<IteratorConstructibleGraph> Traits;

  typedef std::pair<Traits::vertices_size_type, 
    Traits::vertices_size_type> Edge;
  Edge edge_array[] =
    { Edge(0,1), Edge(0,2), Edge(0,3), Edge(0,4), Edge(0,5),
      Edge(1, 2), Edge(1,5), Edge(1,3),
      Edge(2, 4), Edge(2,5),
      Edge(3, 2), 
      Edge(4, 3), Edge(4,1),
      Edge(5, 4) };
  Edge* first = edge_array,
    last = edge_array + sizeof(edge_array)/sizeof(Edge);

  IteratorConstructibleGraph G1(first, last);
  // do something with G1 ...
  
  Traits::vertices_size_type size_V = 6;
  Traits::edges_size_type size_E = sizeof(edge_array)/sizeof(Edge);
  IteratorConstructibleGraph G2(first, last, size_V, size_E);
  // do something with G2 ...
</pre>

<h3>Refinement of</h3>

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

<h3>Notation</h3>

<Table>
<tr>
<td><tt>G</tt></td>
<td>is a graph type that models IteratorConstructibleGraph.</td>
<tr>

<tr>
<td><tt>g</tt></td>
<td>is an object of type <tt>G</tt>.</td>
</tr>

<tr>
<td><tt>first, last</tt></td>
<td>are edge iterators (see above).</td>
</tr>

<tr>
<td><tt>Tr</tt></td>
<td>is an object of type <tt>graph_traits&lt;G&gt;</tt>.</td>
</tr>

<tr>
<td><tt>n_vertices</tt></td>
<td>is an object of type <tt>Tr::vertices_size_type</tt>.</td>
</tr>

<tr>
<td><tt>n_edges</tt></td>
<td>is an object of type <tt>Tr::edges_size_type</tt>.</td>
</tr>

</Table>


<h3>Valid Expressions</h3>

<Table border>

<tr>
<td>
<pre>G g(first, last);</pre>
Construct graph object <tt>g</tt> given an edge range <tt>[first,last)</tt>.
</td>
<tr>

<tr>
<td>
<pre>G g(first, last, n_vertices, n_edges);</pre>
Construct graph object <tt>g</tt> given an edge range
<tt>[first,last)</tt>, the number of vertices, and the number of
edges.  Sometimes this constructor is more efficient than the
constructor lacking the graph size information.
</td>
</tr>

</Table>


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<H3>Concept Checking Class</H3>

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<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="http://www.osl.iu.edu/~lums">Andrew Lumsdaine</A>,
Indiana University (<A
HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
</TD></TR></TABLE>

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