[Boost-users] Compiler error when using property map get()

Subject: [Boost-users] Compiler error when using property map get()
From: Trevor Harmon (Trevor.W.Harmon_at_[hidden])
Date: 2010-07-02 19:41:23

Hi,

The get() function for property maps has me puzzled. Calling it in one  
context gives a compiler error, while in another context it does not.  
A trivial example is below. Note that the code in foo() and main() are  
identical. Any guesses as to why the foo() version gives a compiler  
error while the main() version does not?

FWIW, the error is:

subgraph.cpp: In member function ‘virtual void MyGraph::foo()’:
subgraph.cpp:15: error: conversion from  
‘boost::subgraph_global_property_map<Subgraph*,  
boost::adj_list_edge_property_map<boost::bidirectional_tag, size_t,  
size_t&, size_t, boost::property<boost::edge_index_t, size_t,  
boost::no_property>, boost::edge_index_t>, boost::edge_index_t>’ to  
non-scalar type  
‘boost::adj_list_edge_property_map<boost::bidirectional_tag, size_t,  
size_t&, size_t, boost::property<boost::edge_index_t, size_t,  
boost::no_property>, boost::edge_index_t>’ requested

Thanks,

Trevor

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

using namespace boost;

typedef subgraph<adjacency_list<vecS, vecS, bidirectionalS, int,  
property<edge_index_t, std::size_t> > > Subgraph;
typedef property_map<Subgraph, edge_index_t>::type EdgeIndexMap;

class MyGraph : public Subgraph {
     virtual void foo();
};

void MyGraph::foo() {
     Subgraph g;
     EdgeIndexMap edgeMap = get(edge_index, g);
}

int main(int, char**) {
     Subgraph g;
     EdgeIndexMap edgeMap = get(edge_index, g);
     return 0;
}