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     Copyright (c) Jeremy Siek 2000
    
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<Head>
<Title>MutableGraph</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="sec:MutableGraph"></A>
MutableGraph
</H2>

A MutableGraph can be changed via the addition or removal of
edges and vertices.

<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>e</tt></TD>
<TD>An object of type <tt>boost::graph_traits&lt;G&gt;::edge_descriptor</tt>.</TD>
</TR>

<TR>
<TD><tt>u,v</tt></TD>
<TD>are objects of type <tt>boost::graph_traits&lt;G&gt;::vertex_descriptor</tt>.</TD>
</TR>

<TR>
<TD><tt>iter</tt></TD>
<TD>is an object of type <tt>boost::graph_traits&lt;G&gt;::out_edge_iterator</tt>.</TD>
</TR>

<TR>
<TD><tt>p</tt></TD>
<TD>is an object of a type that models <a
href="http://www.boost.org/sgi/stl/Predicate.html">Predicate</a>
and whose argument type matches the <tt>edge_descriptor</tt> type. 
</TR>

</table>

<H3>Valid Expressions</H3>

<table border>

<tr>
<TD><a name="sec:add-edge"><TT>add_edge(u,&nbsp;v,&nbsp;g)</TT></a></TD>
<TD>
Inserts the edge <i>(u,v)</i> into the graph, and returns an edge
descriptor pointing to the new edge. If the graph disallows parallel
edges, and the edge <i>(u,v)</i> is already in the graph, then the
<tt>bool</tt> flag returned is <tt>false</tt> and the returned edge
descriptor points to the already existing edge.  Note that for
undirected graphs, <i>(u,v)</i> is the same edge as <i>(v,u)</i>, so
after a call to the function <tt>add_edge()</tt>, this implies that
edge <i>(u,v)</i> will appear in the out-edges of <i>u</i> and
<i>(u,v)</i> (or equivalently <i>(v,u)</i>) will appear in the
out-edges of <i>v</i>.  Put another way, <i>v</i> will be adjacent to
<i>u</i> and <i>u</i> will be adjacent to <i>v</i>.
<br>
Return type: <TT>std::pair&lt;edge_descriptor, bool&gt;</TT>
</TD>
</tr>

<tr>
<TD><a name="sec:remove_edge"><TT>remove_edge(u,&nbsp;v,&nbsp;g)</TT></a></TD>
<TD>
Remove the edge <i>(u,v)</i> from the graph. If the
graph allows parallel edges this remove all occurrences of
<i>(u,v)</i>.<br>
Return type: <TT>void</TT><br>
Precondition: <i>u</i> and <i>v</i> are vertices in the graph.<br>
Postcondition: <i>(u,v)</i> is no longer in the edge set for
<TT>g</TT>.<br>
</TD>
</TR>


<tr>
<TD><TT>remove_edge(e,&nbsp;g)</TT></TD>
<TD>Remove the edge <i>e</i> from the graph.<br>
Return type: <TT>void</TT><br>
Precondition: <i>e</i> is an edge in the graph.<br>
Postcondition: <i>e</i> is no longer in the edge set for <TT>g</TT>.
</TD>
</TR>

<tr>
<TD><TT>remove_edge(iter,&nbsp;g)</TT></TD>
<TD>Remove the edge pointed to be <tt>iter</tt> from the graph.  This
expression is only required when the graph also models <a
href="./IncidenceGraph.html">IncidenceGraph</a>.<br>
Return type: <TT>void</TT><br>
Precondition: <tt>*iter</tt> is an edge in the graph.<br>
Postcondition: <tt>*iter</tt> is no longer in the edge set for <TT>g</TT>.
</TD>
</TR>

<tr>
<TD><TT>remove_edge_if(p,&nbsp;g)</TT></TD>
<TD>Remove all the edges from graph <tt>g</tt> for which
the predicate <tt>p</tt> returns true.<br>
Return type: <TT>void</TT>
</TD>
</TR>

<tr>
<TD><TT>remove_out_edge_if(u,&nbsp;p,&nbsp;g)</TT></TD>
<TD>Remove all the out-edges of vertex <tt>u</tt> for which the
predicate <tt>p</tt> returns true. This expression is only required
when the graph also models <a
href="./IncidenceGraph.html">IncidenceGraph</a>.<br>
Return type: <TT>void</TT>
</TD>
</TR>

<tr>
<TD><TT>remove_in_edge_if(u,&nbsp;p,&nbsp;g)</TT></TD>
<TD>Remove all the in-edges of vertex <tt>u</tt> for which the
predicate <tt>p</tt> returns true. This expression is only required when the
graph also models <a
href="./BidirectionalGraph.html">BidirectionalGraph</a>.<br>
Return type: <TT>void</TT>
</TD>
</TR>


<tr>
<TD><a name="sec:add-vertex"><TT>add_vertex(g)</TT></a></TD>
<TD>
Add a new vertex to the graph. The <TT>vertex_descriptor</TT> for the
new vertex is returned.<br>
Return type: <TT>vertex_descriptor</TT>
</TD>
</TR>


<tr>
<TD><TT>clear_vertex(u,&nbsp;g)</TT></TD>
<TD>
Remove all edges to and from vertex <tt>u</tt> from the graph.<br>
Return type: <TT>void</TT><br>
Precondition: <tt>u</tt> is a valid vertex descriptor of <TT>g</TT>.<br>
Postcondition: <tt>u</tt> does not appear as a source or target of
any edge in <TT>g</TT>.
</TD>
</TR>

<tr>
<TD><a name="sec:remove-vertex"><TT>remove_vertex(u,&nbsp;g)</TT></a></TD>
<TD>
Remove <i>u</i> from the vertex set of the graph. Note that undefined
behavior may result if there are edges remaining in the graph who's
target is <i>u</i>. Typically the <TT>clear_vertex()</TT> function
should be called first.<br>
Return type: <TT>void</TT><br>
Precondition: <TT>u</TT> is a valid vertex descriptor of <TT>g</TT>.<br>
Postcondition: <TT>num_vertices(g)</TT> is one less, <TT>u</TT>
no longer appears in the vertex set of the graph and it
is no longer a valid vertex descriptor.
</TD>
</TR>
</TABLE>

<P>
</LI>
</UL>

<P>

<H3>Complexity Guarantees</H3>

<P>

<UL>
<LI>Edge insertion must be either amortized constant time or it
 can be <i>O(log(E/V))</i> if the insertion also checks to
  prevent the addition of parallel edges (which is a ``feature'' of
  some graph types).
</LI>
<LI>Edge removal is guaranteed to be <i>O(E)</i>.</LI>
<LI>Vertex insertion is guaranteed to be amortized constant time.</LI>
<LI>Clearing a vertex is <i>O(E + V)</i>.</LI>
<LI>Vertex removal is <i>O(E + V)</i>.</LI>
</UL>

<H3>Models</H3>

<UL>
<LI><TT>adjacency_list</TT>
</LI>
</UL>


<H3>Concept Checking Class</H3>

<PRE>
  template &lt;class G&gt;
  struct MutableGraphConcept
  {
    typedef typename boost::graph_traits&lt;G&gt;::edge_descriptor edge_descriptor;
    void constraints() {
      v = add_vertex(g);
      clear_vertex(v, g);
      remove_vertex(v, g);
      e_b = add_edge(u, v, g);
      remove_edge(u, v, g);
      remove_edge(e, g);
    }
    G g;
    edge_descriptor e;
    std::pair&lt;edge_descriptor, bool&gt; e_b;
    typename boost::graph_traits&lt;G&gt;::vertex_descriptor u, v;
    typename boost::graph_traits&lt;G&gt;::out_edge_iterator iter;
  };

  template &lt;class edge_descriptor&gt;
  struct dummy_edge_predicate {
    bool operator()(const edge_descriptor& e) const {
      return false;
    }
  };

  template &lt;class G&gt;
  struct MutableIncidenceGraphConcept
  {
    void constraints() {
      BOOST_CONCEPT_ASSERT(( MutableGraph&lt;G&gt; ));
      remove_edge(iter, g);
      remove_out_edge_if(u, p, g);
    }
    G g;
    typedef typename boost::graph_traits&lt;G&gt;::edge_descriptor edge_descriptor;
    dummy_edge_predicate&lt;edge_descriptor&gt; p;
    typename boost::graph_traits&lt;G&gt;::vertex_descriptor u;
    typename boost::graph_traits&lt;G&gt;::out_edge_iterator iter;
  };

  template &lt;class G&gt;
  struct MutableBidirectionalGraphConcept
  {
    void constraints() {
      BOOST_CONCEPT_ASSERT(( MutableIncidenceGraph&lt;G&gt; ));
      remove_in_edge_if(u, p, g);
    }
    G g;
    typedef typename boost::graph_traits&lt;G&gt;::edge_descriptor edge_descriptor;
    dummy_edge_predicate&lt;edge_descriptor&gt; p;
    typename boost::graph_traits&lt;G&gt;::vertex_descriptor u;
  };

  template &lt;class G&gt;
  struct MutableEdgeListGraphConcept
  {
    void constraints() {
      BOOST_CONCEPT_ASSERT(( MutableGraph&lt;G&gt; ));
      remove_edge_if(p, g);
    }
    G g;
    typedef typename boost::graph_traits&lt;G&gt;::edge_descriptor edge_descriptor;
    dummy_edge_predicate&lt;edge_descriptor&gt; p;
  };
</PRE>

<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>)
</TD></TR></TABLE>

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