Re: [Boost-users] [BGL] Bundled properties and property maps

Subject: Re: [Boost-users] [BGL] Bundled properties and property maps
From: Dmitry Bufistov (dmitry_at_[hidden])
Date: 2008-12-17 18:05:25

Geoff Hilton escribió:
> 
> Note: graph variable is of type const Graph&.
> 
[skip]
> 
> Also, my Weight type has an explicit constructor which takes a POD 
> convertible to 0, a requirement imposed it seems by line 155 of 
> bellman_ford_shortest_paths.hpp. Why doesn't the algorithm take a weight 
> of value zero as a parameter and use it instead?
> 
> Anyway, because of this explicit constructor I've added a (typical) 
> assignment operator (not sure if this is relevant, but I'm mentioning it 
> just in case).
> 
> I should also note that out of curiosity I commented out line 103 of 
> bellman_ford_shortest_paths.hpp which is:
> 
> function_requires<ReadablePropertyMapConcept<WeightMap, Edge> >();
> 
> Commenting out the above line allows my code as written above to 
> compile, otherwise it fails with the error written in my original 
> response (quoted above). Whether the compiled code (with line 103 
> commented out) functions as expected  I don't know, I haven't tested it.
> 
> Thanks,
> Geoff

It looks like the problem is with
template <class PMap, class Key> struct ReadablePropertyMapConcept;

The following code fails to compile:

#include <boost/graph/graph_concepts.hpp>
#include <boost/graph/adjacency_list.hpp>

using namespace boost;
struct EdgeProp
{
         double weight;
};

typedef boost::adjacency_list<vecS, vecS, directedS, no_property, 
EdgeProp > graph_t;
int main()
{
         typedef boost::property_map<graph_t, double 
EdgeProp::*>::const_type WeightMap;
         typedef boost::graph_traits<graph_t>::edge_descriptor Edge;
         function_requires<ReadablePropertyMapConcept<WeightMap, Edge> >();
}

You may try to change the boost/property_map.hpp as follows:
(in the version 1.37 the line number is 165)
typename typename property_traits<PMap>::value_type val;
to the
typename remove_const<typename property_traits<PMap>::value_type>::type val;

Does it work for you?

Regards,
Dmitry