Thanks for your help.  Getting a little closer.<div><br></div><div>Once I get the edge properties working I&#39;ll look at traversal concepts other than AdjacencyGraphs.  So far this has been the easy part for me.</div><div>
<br></div><div>I have been looking at the grid graph, but I couldn&#39;t figure out how to add weights to the edges of a grid graph.  I can&#39;t find a simple example of an implicit graph with properties.  (Which is why I&#39;m trying to write one now.)</div>
<div><br></div><div>What do you mean by &quot;Write an empty struct that inherits from all of the ones that you are going to model&quot;?  I didn&#39;t think there were concept base classes to inherit from.</div><div><br>
</div><div>Changing the property typedef in the implicit graph struct to </div><div><br></div><div>    typedef boost::property&lt;boost::edge_weight_t, float&gt; edge_property_type;</div><div><br></div><div>making the get() functions take constant graph object references, and checking against the ReadablePropertyGraphConcept improves the compilation.  I now no longer have pages of errors, which makes me think I&#39;m on the right track.</div>
<div><br></div><div>I still have two errors, both of which I&#39;m confused about.</div><div><br></div><div>1. graph_concepts.hpp:390: error: conversion from ‘EdgeWeightMap’ to non-scalar type ‘boost::typed_identity_property_map&lt;size_t&gt;’ requested</div>
<div><br></div><div>This is the same as before.  This error makes me feel like I&#39;ve got the wrong return value for one of my get() functions, but after double-checking they look right.</div><div><br></div><div><br></div>
<div>2. property_map.hpp:318: error: no match for ‘operator[]’ in ‘(const boost::typed_identity_property_map&lt;size_t&gt;&amp;)((const boost::typed_identity_property_map&lt;size_t&gt;*)(&amp; pa))[k]’</div><div><br></div>
<div>I didn&#39;t think any concept required operator[], so I&#39;m not sure why this is happening.  Line 318 is inside the inline get() function of the put_get_helper(), but I&#39;m not using put_get_helper() in my code.</div>
<div><br></div><div><br><div class="gmail_quote">On Thu, Jun 24, 2010 at 1:25 PM, W.P. McNeill <span dir="ltr">&lt;<a href="mailto:billmcn@gmail.com">billmcn@gmail.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
I am writing a stripped-down implicit graph that I hope can be a useful template for others working with the Boost Graph library.  The project is hosted at github.  Excerpts from the source are in this email, and the full source is viewable online at <a href="http://github.com/wpm/Boost-Implicit-Graph-Example" target="_blank">http://github.com/wpm/Boost-Implicit-Graph-Example</a>.<div>

<br></div><div>I am currently getting errors from the concept checking code which I don&#39;t understand and am looking for suggestions as to what I am doing wrong.</div><div><br></div><div>This is graph class.</div><div>

<br></div><div><div>struct ImplicitRingGraph {</div><div><span style="white-space:pre-wrap">	</span>ImplicitRingGraph(size_t n):n(n) {};</div><div><br></div><div><span style="white-space:pre-wrap">	</span>// Graph concept</div>

<div><span style="white-space:pre-wrap">	</span>typedef size_t vertex_descriptor;</div><div><span style="white-space:pre-wrap">	</span>typedef boost::undirected_tag directed_category;</div>
<div><span style="white-space:pre-wrap">	</span>typedef boost::disallow_parallel_edge_tag edge_parallel_category;</div><div><span style="white-space:pre-wrap">	</span>typedef boost::adjacency_graph_tag traversal_category;</div>

<div><br></div><div><span style="white-space:pre-wrap">	</span>// AdjacencyGraph concept</div><div><span style="white-space:pre-wrap">	</span>typedef RingAdjacencyIterator adjacency_iterator;</div>
<div><br></div><div><span style="white-space:pre-wrap">	</span>// PropertyGraph concept</div><div><span style="white-space:pre-wrap">	</span>typedef boost::edge_weight_t edge_property_type;</div>
<div><br></div><div><span style="white-space:pre-wrap">	</span>// Additional types required by the concept-checking code.</div><div><span style="white-space:pre-wrap">	</span>typedef std::pair&lt;vertex_descriptor, vertex_descriptor&gt; edge_descriptor;</div>

<div><span style="white-space:pre-wrap">	</span>typedef size_t vertices_size_type;</div><div><span style="white-space:pre-wrap">	</span>typedef size_t edges_size_type;</div><div><span style="white-space:pre-wrap">	</span>typedef size_t degree_size_type;</div>

<div><span style="white-space:pre-wrap">	</span></div><div><span style="white-space:pre-wrap">	</span>typedef void out_edge_iterator;</div><div><span style="white-space:pre-wrap">	</span>typedef void in_edge_iterator;</div>

<div><span style="white-space:pre-wrap">	</span>typedef void vertex_iterator;</div><div><span style="white-space:pre-wrap">	</span>typedef void edge_iterator;</div><div><br></div><div><span style="white-space:pre-wrap">	</span>// The number of vertices in the graph.</div>

<div><span style="white-space:pre-wrap">	</span>size_t n;</div><div>};</div></div><div><div>typedef boost::graph_traits&lt;ImplicitRingGraph&gt;::edge_descriptor Edge;</div></div><div><br></div><div><br>
</div><div>I want the edges to have weights, so it models the PropertyGraph concept.  The following functions implement the valid expressions.</div><div><br></div><div><br></div><div><div>EdgeWeightMap get(boost::edge_weight_t, ImplicitRingGraph&amp; g) {</div>

<div><span style="white-space:pre-wrap">	</span>return EdgeWeightMap();</div><div>}</div><div><br></div><div><br></div><div>EdgeWeight get(boost::edge_weight_t tag, ImplicitRingGraph&amp; g, Edge e) {</div>
<div><span style="white-space:pre-wrap">	</span>return get(tag, g)[e];</div><div>}</div></div><div><br></div><div><br></div><div>(Definitions of Edge, EdgeWeight, and EdgeWeightMap are visible online.  I also define an adjacency iterator that is not shown here.)</div>

<div><div><br></div></div><div>I can write code that reads an edge weight.</div><div><span style="white-space:pre-wrap"><br></span></div><div><span style="white-space:pre-wrap"><span style="white-space:normal"><span style="white-space:pre-wrap">	</span></span>ImplicitRingGraph g(5);</span> </div>

<div><div><span style="white-space:pre-wrap">	</span>EdgeWeightMap m = get(boost::edge_weight, g);</div><div><span style="white-space:pre-wrap">	</span>boost::graph_traits&lt;ImplicitRingGraph&gt;::edge_descriptor e(0, 1);</div>

<div><span style="white-space:pre-wrap">	</span>EdgeWeight w = get(boost::edge_weight, g, e);</div></div><div><br></div><div>However I get errors when I try to use the concept checking code.</div><div><br>
</div><div><div><span style="white-space:pre-wrap">	</span>function_requires&lt; </div><div><span style="white-space:pre-wrap">		</span>PropertyGraphConcept&lt;ImplicitRingGraph,</div><div>
<span style="white-space:pre-wrap">							</span> Edge,</div><div><span style="white-space:pre-wrap">							</span> edge_weight_t&gt;</div><div><span style="white-space:pre-wrap">	</span>&gt;();</div>
</div><div><br></div><div><br></div><div>The full error printout is huge, but there appear to be three relevant problems.</div><div><br></div><div><div>1. graph_concepts.hpp:406: error: conversion from ‘EdgeWeightMap’ to non-scalar type ‘boost::typed_identity_property_map&lt;size_t&gt;’ requested</div>

<div><br></div><div><div>The line in graph_concepts.hpp is</div><div><br></div><div><div>        Map pmap = get(Property(), g);</div></div><div><br></div><div>inside the concept check for PropertyGraph.  It looks to me like I have a function to handle this.  I don&#39;t understand where boost::typed_identity_property_map&lt;size_t&gt; is coming from.</div>

</div><div><br></div><div><br></div><div>2. graph_concepts.hpp:408: error: no matching function for call to ‘put(boost::edge_weight_t, ImplicitRingGraph&amp;, Edge&amp;, size_t&amp;)’</div></div><div><br></div><div>I didn&#39;t write any put() functions so I understand why I&#39;m getting this.  However, I would like the edge weights to be readable but not writeable (myEdgeWeightMap models a ReadablePropertyMap), and I can&#39;t figure out how to specify the read-only property in the graph defintion.</div>

<div><br></div><div><br></div><div>3. graph_concepts.hpp:390: error: no matching function for call to ‘get(boost::edge_weight_t, const ImplicitRingGraph&amp;)’</div><div>graph_concepts.hpp:391: error: no matching function for call to ‘get(boost::edge_weight_t, const ImplicitRingGraph&amp;, Edge&amp;)’</div>

<div><br></div><div>Should I create functions identical to what  I&#39;ve already written, except with constant modifiers in front of the graph type?  That feels like redundant source.</div><div><br></div><div><br></div>
<div>
Thanks for any help you can give.  Hopefully, a completed version of this example would be a useful resource for other BGL developers.</div>
</blockquote></div><br></div>