Re: [Boost-users] BGL: shared_ptr as bundled properties > how to generate properties maps ???

Subject: Re: [Boost-users] BGL: shared_ptr as bundled properties > how to generate properties maps ???
From: Damien Maupu (damien.maupu_at_[hidden])
Date: 2010-01-11 09:24:10

Hi,

It's me one more time.
I am still quite new to metaprogramming.

I don't understand how you have a functor that "take an edge descriptor".
Can you give me such example of functor?
In the link you send me on "function_property_map" how should be written 
"get_weight" ?

Thank you

Damien

Jeremiah Willcock a écrit :
> On Wed, 6 Jan 2010, Damien Maupu wrote:
>
>   
>> Dear all,
>>
>> I am using bundled properties when I define my graph.
>> The bundled properties are smart pointers to my own class Edge and Vertex.
>> I write something like:
>> typedef boost::shared_ptr<Vertex> VertexPtr;
>> typedef boost::shared_ptr<Edge> EdgePtr;
>> typedef adjacency_list<vecS, vecS, directedS, VertexPtr, EdgePtr>    Graph;
>>
>> Vertex and Edge being my own classes to store information on the vertices and 
>> the edges.
>> For what I read in the doc, this is the correct, more modern way to do it.
>>
>> My problem is the following.
>> I am trying to use the BGL algorithms and some of them require vertex/edge 
>> info to be provide as properties maps.
>>
>> From http://www.boost.org/doc/libs/1_41_0/libs/graph/doc/bundles.html
>> I know it is possible to generate those maps from bundled properties.
>>
>> It works well if I don't use shared_ptr but cannot compile otherwise.
>>
>> When using shared_ptr, similarly to the doc, I wrote:
>>
>> typedef property_map<SearchGraph, float EdgePtr::*>::type WeightMap;
>> WeightMap weightMap = get(&EdgePtr::m_cost, *_graph);
>>
>> m_cost being a public float member of my own class Edge.
>>
>> I have the following compilation error:
>> 'm_cost' : is not a member of 'boost::shared_ptr<T>'
>>
>> Indeed it is not.
>> My question is, I can let the shared_ptr access the member?
>> In other world how to deal with bundled properties / properties maps and 
>> shared_ptr.
>>
>> Extra question, could 'm_cost' be a private member of my own class Edge?
>>     
>
> Try writing a function that takes an edge descriptor and returns a 
> reference to m_cost for that edge (using the bundled property syntax), 
> then using the code in 
> <URL:http://article.gmane.org/gmane.comp.lib.boost.user/54397> to convert 
> that into a property map.
>
> BTW, sorry about referring to this message before I sent it (this is the 
> one I was referring to about handling pointers as bundled properties).  I 
> thought I had sent it earlier.
>
> -- Jeremiah Willcock
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