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Alex Brooks | 18 Nov 12:37
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[BGL] Bundled properties and property maps

Hi,

I've used BGL before for representing graphs, but this is my first time with 
an algorithm.  I've been stuck for many hours trying to define a property map 
with bundled properties, I'd really appreciate some help.  I'm using gcc4.3, 
boost 1.34.  An example program and the compiler error are:

-------------------------------------------------------------
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/astar_search.hpp>

using namespace std;

class Point {
public:
    double p_[2];
};

struct EdgeProp {
    double cost;
};

typedef boost::adjacency_list<boost::vecS,
                              boost::vecS,
                              boost::undirectedS,
                              Point*,
                              EdgeProp> Graph;

typedef boost::graph_traits<Graph>::vertex_descriptor VertexRef;
(Continue reading)

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Andrew Sutton | 18 Nov 19:28

Re: [BGL] Bundled properties and property maps

Does anyone know what might be wrong?

Yes... The type of the property map generated by the get() function is built for a *const* graph (since you're passing graph as const&), but your're declaring EdgeWeightMap over a non-const graph (as in property_map<Graph, ...>). I think the most appropriate fix is to change the definition of EdgeWeightMap to
 
   typedef boost::property_map<const Graph, double const EdgeProp::*>::type EdgeWeightMap;

Another solution might be to always pass by non-const reference, but that's not really good style. I would have thought that property_map was appropriately specialized for const/non-const versions. I'll have to look into it.

More generally, I'm a bit mystefied by the "<Graph, double EdgeProp::*>::type"
syntax -- can anyone give me any pointers about what this syntax means, or
where I can look it up? (googling for colon-colon-star doesn't help much).
I also tried pattern-matching from the documentation page about bundled
properties (the weight_map(get(&Highway::miles, map)) example) but couldn't
get this to compile either.  Is this example correct?

It's pointer-to-member syntax. Read from right to left You're saying that the type is a "pointer to a member of EdgeProp that is of type double." Or in this case, a pointer to a const EdgeProp that's a double.

Andrew Sutton
andrew.n.sutton <at> gmail.com
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Alex Brooks | 19 Nov 00:23
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Re: [BGL] Bundled properties and property maps

Hi Andrew,

Thanks very much for the help, I've got it working now.  I had to use a 
non-const reference though.  Here are the options I tried:

// Option A:
    Graph &nonConstGraph = const_cast<Graph&>(graph);
    typedef boost::property_map<Graph, double EdgeProp::*>::type 
EdgeWeightMap; 
    EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, nonConstGraph);

// Option B:
//     typedef boost::property_map<Graph, double const EdgeProp::*>::type 
EdgeWeightMap; 
//     EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, graph);

Option A works, but is a bit ugly.
Option B is what you suggested, but it gives the following error:

/home/a.brooks/shh/src/libs/prm/test/stupid.cpp:70: error: conversion 
from 'boost::bundle_property_map<const boost::adjacency_list<boost::vecS, 
boost::vecS, boost::undirectedS, Point*, EdgeProp, boost::no_property, 
boost::listS>, boost::detail::edge_desc_impl<boost::undirected_tag, unsigned 
int>, EdgeProp, const double>' to non-scalar type 'searchThroughGraph(const 
Graph&, VertexRef, VertexRef, std::vector<unsigned int, 
std::allocator<unsigned int> >&)::EdgeWeightMap' requested

Do I also need to modify the 'get()' line?

> It's pointer-to-member syntax. Read from right to left You're saying that
> the type is a "pointer to a member of EdgeProp that is of type double." Or
> in this case, a pointer to a const EdgeProp that's a double.

Awesome, thanks for the pointer.

Cheers,

Alex
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Andrew Sutton | 19 Nov 01:22

Re: [BGL] Bundled properties and property maps



//     typedef boost::property_map<Graph, double const EdgeProp::*>::type
EdgeWeightMap;
//     EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, graph);

Option A works, but is a bit ugly.
Option B is what you suggested, but it gives the following error:

Gotta a const Graph also:

property_map<const Graph, double const EdgeProp::*>

Andrew Sutton
andrew.n.sutton <at> gmail.com
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Alex Brooks | 19 Nov 01:37
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Re: [BGL] Bundled properties and property maps

> Gotta a const Graph also:
>
> property_map<const Graph, double const EdgeProp::*>

This line compiles now, but I get a new compile error from the astar_search 
line.  The important bits are:

    typedef boost::property_map<const Graph, double const EdgeProp::*>::type 
EdgeWeightMap; 
    EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, graph);

    std::vector<VertexRef> predecessors(num_vertices(graph));
    astar_search( graph,
                  start,
                  aStarHeuristic,
                  boost::weight_map(edgeWeightMap).
                  predecessor_map(&predecessors[0]).
                  visitor(aStarVisitor) );

The error is:

/usr/include/c++/4.3/bits/allocator.h:84:   instantiated 
from 'std::allocator<const double>'
/usr/include/c++/4.3/bits/stl_vector.h:75:   instantiated 
from 'std::_Vector_base<const double, std::allocator<const double> >'
/usr/include/c++/4.3/bits/stl_vector.h:176:   instantiated 
from 'std::vector<const double, std::allocator<const double> >'
/usr/include/boost/graph/astar_search.hpp:360:   instantiated from 'void 
boost::detail::astar_dispatch1(VertexListGraph&, typename 
boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, CostMap, 
DistanceMap, WeightMap, IndexMap, ColorMap, const Params&) [with 
VertexListGraph = const boost::adjacency_list<boost::vecS, boost::vecS, 
boost::undirectedS, Point*, EdgeProp, boost::no_property, boost::listS>, 
AStarHeuristic = AStarHeuristic, CostMap = 
boost::detail::error_property_not_found, DistanceMap = 
boost::detail::error_property_not_found, WeightMap = 
boost::bundle_property_map<const boost::adjacency_list<boost::vecS, 
boost::vecS, boost::undirectedS, Point*, EdgeProp, boost::no_property, 
boost::listS>, boost::detail::edge_desc_impl<boost::undirected_tag, unsigned 
int>, EdgeProp, const double>, IndexMap = 
boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_bundle_t, 
Point*, boost::no_property>, unsigned int>, ColorMap = 
boost::detail::error_property_not_found, Params = 
boost::bgl_named_params<AStarVisitor, boost::graph_visitor_t, 
boost::bgl_named_params<unsigned int*, boost::vertex_predecessor_t, 
boost::bgl_named_params<boost::bundle_property_map<const 
boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
EdgeProp, boost::no_property, boost::listS>, 
boost::detail::edge_desc_impl<boost::undirected_tag, unsigned int>, EdgeProp, 
const double>, boost::edge_weight_t, boost::no_property> > >]'
/usr/include/boost/graph/astar_search.hpp:394:   instantiated from 'void 
boost::astar_search(VertexListGraph&, typename 
boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, const 
boost::bgl_named_params<P, T, R>&) [with VertexListGraph = const 
boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
EdgeProp, boost::no_property, boost::listS>, AStarHeuristic = AStarHeuristic, 
P = AStarVisitor, T = boost::graph_visitor_t, R = 
boost::bgl_named_params<unsigned int*, boost::vertex_predecessor_t, 
boost::bgl_named_params<boost::bundle_property_map<const 
boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
EdgeProp, boost::no_property, boost::listS>, 
boost::detail::edge_desc_impl<boost::undirected_tag, unsigned int>, EdgeProp, 
const double>, boost::edge_weight_t, boost::no_property> >]'
/home/a.brooks/shh/src/libs/prm/test/stupid.cpp:83:   instantiated from here
/usr/include/c++/4.3/ext/new_allocator.h:82: error: 'const _Tp* 
__gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const 
double]' cannot be overloaded
/usr/include/c++/4.3/ext/new_allocator.h:79: error: with '_Tp* 
__gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const double]'

Any other ideas?

Thanks again,

Alex
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Dmitry Bufistov | 19 Nov 05:12
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Re: [BGL] Bundled properties and property maps

Hi Alex,

I was able to compile your original code by changing the line
typedef boost::property_map<Graph, double EdgeProp::*>::type  EdgeWeightMap;
to
typedef boost::property_map<Graph, double EdgeProp::*>::const_type 
EdgeWeightMap;

hope this will help,
Dmitry

Alex Brooks escribió:
>> Gotta a const Graph also:
>>
>> property_map<const Graph, double const EdgeProp::*>
> 

> 
> Any other ideas?
> 
> 
> Thanks again,
> 
> Alex
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Andrew Sutton | 19 Nov 14:25

Re: [BGL] Bundled properties and property maps

I was able to compile your original code by changing the line
typedef boost::property_map<Graph, double EdgeProp::*>::type  EdgeWeightMap;
to
typedef boost::property_map<Graph, double EdgeProp::*>::const_type EdgeWeightMap;

That's right! I had completely forgotten about the const_type member... Good catch Dmitry.
 
Andrew Sutton
andrew.n.sutton <at> gmail.com
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Andrew Sutton | 19 Nov 14:34

Re: [BGL] Bundled properties and property maps



/usr/include/c++/4.3/ext/new_allocator.h:82: error: 'const _Tp*
__gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const
double]' cannot be overloaded
/usr/include/c++/4.3/ext/new_allocator.h:79: error: with '_Tp*
__gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const double]'


Not good... astar passes its graph by non-const reference so when it declares:

      typedef typename property_traits<WeightMap>::value_type D;
      typename std::vector<D>::size_type

D is apparently const double, and std::vector<const double> doesn't seem to work too well - not to mention the fact that you probably want to assign values to elemetns of that vector :) I guess your only solution is to pass the graph by non-const reference.

This may be a bug, but I'm not entirely sure.

Andrew Sutton
andrew.n.sutton <at> gmail.com
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Alex Brooks | 20 Nov 00:47
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Re: [BGL] Bundled properties and property maps

Hi Andrew/Dmitry,

Thanks again for the help.  I guess I'll stick with the const-cast.

Cheers,

Alex
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Geoff Hilton | 17 Dec 02:38

Re: [BGL] Bundled properties and property maps

Alex Brooks wrote:
>> Gotta a const Graph also:
>>
>> property_map<const Graph, double const EdgeProp::*>
> 
> This line compiles now, but I get a new compile error from the astar_search 
> line.  The important bits are:
> 
>     typedef boost::property_map<const Graph, double const EdgeProp::*>::type 
> EdgeWeightMap; 
>     EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, graph);
> 
>     std::vector<VertexRef> predecessors(num_vertices(graph));
>     astar_search( graph,
>                   start,
>                   aStarHeuristic,
>                   boost::weight_map(edgeWeightMap).
>                   predecessor_map(&predecessors[0]).
>                   visitor(aStarVisitor) );
> 
> The error is:
> 
> /usr/include/c++/4.3/bits/allocator.h:84:   instantiated 
> from 'std::allocator<const double>'
> /usr/include/c++/4.3/bits/stl_vector.h:75:   instantiated 
> from 'std::_Vector_base<const double, std::allocator<const double> >'
> /usr/include/c++/4.3/bits/stl_vector.h:176:   instantiated 
> from 'std::vector<const double, std::allocator<const double> >'
> /usr/include/boost/graph/astar_search.hpp:360:   instantiated from 'void 
> boost::detail::astar_dispatch1(VertexListGraph&, typename 
> boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, CostMap, 
> DistanceMap, WeightMap, IndexMap, ColorMap, const Params&) [with 
> VertexListGraph = const boost::adjacency_list<boost::vecS, boost::vecS, 
> boost::undirectedS, Point*, EdgeProp, boost::no_property, boost::listS>, 
> AStarHeuristic = AStarHeuristic, CostMap = 
> boost::detail::error_property_not_found, DistanceMap = 
> boost::detail::error_property_not_found, WeightMap = 
> boost::bundle_property_map<const boost::adjacency_list<boost::vecS, 
> boost::vecS, boost::undirectedS, Point*, EdgeProp, boost::no_property, 
> boost::listS>, boost::detail::edge_desc_impl<boost::undirected_tag, unsigned 
> int>, EdgeProp, const double>, IndexMap = 
> boost::vec_adj_list_vertex_id_map<boost::property<boost::vertex_bundle_t, 
> Point*, boost::no_property>, unsigned int>, ColorMap = 
> boost::detail::error_property_not_found, Params = 
> boost::bgl_named_params<AStarVisitor, boost::graph_visitor_t, 
> boost::bgl_named_params<unsigned int*, boost::vertex_predecessor_t, 
> boost::bgl_named_params<boost::bundle_property_map<const 
> boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
> EdgeProp, boost::no_property, boost::listS>, 
> boost::detail::edge_desc_impl<boost::undirected_tag, unsigned int>, EdgeProp, 
> const double>, boost::edge_weight_t, boost::no_property> > >]'
> /usr/include/boost/graph/astar_search.hpp:394:   instantiated from 'void 
> boost::astar_search(VertexListGraph&, typename 
> boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, const 
> boost::bgl_named_params<P, T, R>&) [with VertexListGraph = const 
> boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
> EdgeProp, boost::no_property, boost::listS>, AStarHeuristic = AStarHeuristic, 
> P = AStarVisitor, T = boost::graph_visitor_t, R = 
> boost::bgl_named_params<unsigned int*, boost::vertex_predecessor_t, 
> boost::bgl_named_params<boost::bundle_property_map<const 
> boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Point*, 
> EdgeProp, boost::no_property, boost::listS>, 
> boost::detail::edge_desc_impl<boost::undirected_tag, unsigned int>, EdgeProp, 
> const double>, boost::edge_weight_t, boost::no_property> >]'
> /home/a.brooks/shh/src/libs/prm/test/stupid.cpp:83:   instantiated from here
> /usr/include/c++/4.3/ext/new_allocator.h:82: error: 'const _Tp* 
> __gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const 
> double]' cannot be overloaded
> /usr/include/c++/4.3/ext/new_allocator.h:79: error: with '_Tp* 
> __gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const double]'
> 
> 
> Any other ideas?
> 
> 
> Thanks again,
> 
> Alex

I'm having the same problem though mine (with MSVC9) says:

error C2678: binary '=': no operator found which takes a left-hand 
operand of type 'const Weight' (or there is no acceptable conversion) 
c:\program files\boost\boost_1_37_0\boost\property_map.hpp	161

A follow-up would be greatly appreciated.

Thanks,
Geoff
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Dmitry Bufistov | 17 Dec 11:12
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Re: [BGL] Bundled properties and property maps

Geoff Hilton wrote:
> 
> 
> I'm having the same problem though mine (with MSVC9) says:
> 
> error C2678: binary '=': no operator found which takes a left-hand 
> operand of type 'const Weight' (or there is no acceptable conversion) 
> c:\program files\boost\boost_1_37_0\boost\property_map.hpp    161
> 
> 
> A follow-up would be greatly appreciated.
> 
> Thanks,
> Geoff

You can try to use
boost::remove_const<Weight>::type

Regards,
Dmitry
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Geoff Hilton | 17 Dec 17:03

Re: [BGL] Bundled properties and property maps

Dmitry Bufistov wrote:
> Geoff Hilton wrote:
>>
>>
>> I'm having the same problem though mine (with MSVC9) says:
>>
>> error C2678: binary '=': no operator found which takes a left-hand 
>> operand of type 'const Weight' (or there is no acceptable conversion) 
>> c:\program files\boost\boost_1_37_0\boost\property_map.hpp    161
>>
>>
>> A follow-up would be greatly appreciated.
>>
>> Thanks,
>> Geoff
> 
> You can try to use
> boost::remove_const<Weight>::type
> 
> Regards,
> Dmitry

I appreciate your suggestion, but the reason I'm getting the error is 
because I'm trying to make the code const-correct, until yesterday code 
that raised this issue would have the graph parameter be rendered 
non-const as a temporary "fix", but that's not good style, I'm looking 
to remedy this by making the code const-correct now. :)

If there's no other solution then I'll revert the const-correctedness 
changes until there is one, but I have a hard time believing this to be 
the case.

Thanks,
Geoff
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Dmitry Bufistov | 17 Dec 19:02
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Re: [BGL] Bundled properties and property maps

Geoff Hilton wrote:
> 
> 
> 
> I appreciate your suggestion, but the reason I'm getting the error is 
> because I'm trying to make the code const-correct, 

Just a quick glance at your code would be greatly appreciated,

Regards,
Dmitry
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Geoff Hilton | 17 Dec 19:30

Re: [BGL] Bundled properties and property maps

Dmitry Bufistov wrote:
> Geoff Hilton wrote:
>>
>>
>> I'm having the same problem though mine (with MSVC9) says:
>>
>> error C2678: binary '=': no operator found which takes a left-hand 
>> operand of type 'const Weight' (or there is no acceptable conversion) 
>> c:\program files\boost\boost_1_37_0\boost\property_map.hpp    161
>>
>>
>> A follow-up would be greatly appreciated.
>>
>> Thanks,
>> Geoff
> 
> You can try to use
> boost::remove_const<Weight>::type
> 
> Regards,
> Dmitry

To help things along, here's the code in question:

Note: graph variable is of type const Graph&.

const boost::property_map<Graph,
     Weight EdgeProp::*>::const_type eprop = 
boost::get(&EdgeProp::weight, graph);

const boost::property_map<Graph,
     boost::vertex_index_t>::const_type vindex = 
boost::get(boost::vertex_index, graph);
const vertex_descriptor firstVertex = *GetGraphBeginVertexIterator(graph);

PredecessorMap preds = PredecessorMap(numVertices);
DistanceMap dists = DistanceMap(numVertices);
boost::bellman_ford_shortest_paths(graph, numVertices,
     weight_map(eprop)
     .predecessor_map(boost::make_iterator_property_map(preds.begin(), 
vindex))
     .distance_map(boost::make_iterator_property_map(dists.begin(), vindex))
     .root_vertex(firstVertex)
     .distance_combine(Combiner())
     .distance_compare(Comparer(currentOffset))
);

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
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Dmitry Bufistov | 18 Dec 00:05
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Re: [BGL] Bundled properties and property maps

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
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Geoff Hilton | 18 Dec 17:48

Re: [BGL] Bundled properties and property maps

Dmitry Bufistov wrote:
> 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

Thanks Dmitry, it does work! I do wonder though, isn't there a better 
fix? What about specializing ReadablePropertyMapConcept specifically for 
const properties, or does that not make sense with concept classes? I'm 
okay with modifying BGL code, but the remove_const makes me feel dirty.

This sounds like something that should be brought up with BGL maintainers...

Geoff
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Dmitry Bufistov | 18 Dec 22:17
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Re: [BGL] Bundled properties and property maps

Geoff Hilton escribió:
> 
>> (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
> 
> Thanks Dmitry, it does work! I do wonder though, isn't there a better 
> fix? What about specializing ReadablePropertyMapConcept specifically for 
> const properties, or does that not make sense with concept classes? I'm 
> okay with modifying BGL code, but the remove_const makes me feel dirty.
> 
> This sounds like something that should be brought up with BGL 
> maintainers...
> 
> Geoff

I believe that something is bad with the const version of 
bundled_properties. Andrew, what do you think?

Dmitry
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Andrew Sutton | 19 Dec 02:37

Re: [BGL] Bundled properties and property maps


Thanks Dmitry, it does work! I do wonder though, isn't there a better fix? What about specializing ReadablePropertyMapConcept specifically for const properties, or does that not make sense with concept classes? I'm okay with modifying BGL code, but the remove_const makes me feel dirty.

This sounds like something that should be brought up with BGL maintainers...

Geoff

I believe that something is bad with the const version of bundled_properties. Andrew, what do you think?

This is the only report - to my knowledge - of this kind of problem. I'm not entirely that the best solution is to change the BGL. I'll have to take a good look tomorrow morning.
 
Andrew Sutton
andrew.n.sutton <at> gmail.com
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Geoff Hilton | 5 Jan 15:48

Re: [BGL] Bundled properties and property maps

Andrew Sutton wrote:
> 
>         Thanks Dmitry, it does work! I do wonder though, isn't there a
>         better fix? What about specializing ReadablePropertyMapConcept
>         specifically for const properties, or does that not make sense
>         with concept classes? I'm okay with modifying BGL code, but the
>         remove_const makes me feel dirty.
> 
>         This sounds like something that should be brought up with BGL
>         maintainers...
> 
>         Geoff
> 
> 
>     I believe that something is bad with the const version of
>     bundled_properties. Andrew, what do you think?
> 
> 
> This is the only report - to my knowledge - of this kind of problem. I'm 
> not entirely that the best solution is to change the BGL. I'll have to 
> take a good look tomorrow morning.
>  
> Andrew Sutton
> andrew.n.sutton <at> gmail.com

Merry Christmas, Happy New Year and all that!
Any progress?

Thanks,
Geoff
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Alex Brooks | 18 Nov 13:02
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[BGL] Bundled properties and property maps

Sorry, I neglected to point out the line that doesn't compile.  It's marked 
below:

  typedef boost::property_map<Graph, double EdgeProp::*>::type EdgeWeightMap;
  // The following line fails to compile
  EdgeWeightMap edgeWeightMap = get(&EdgeProp::cost, graph);

Thanks again,

Alex
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Gmane